In Athens, the population was divided into four classes based on wealth, with some political offices reserved for members of the higher levels, although people could change classes if they made more money. In Sparta, all men carried the title of “equal” if they finished their education. However, the Spartan “kings,” who served as the state’s dual military and religious leaders, came from two families.


Slaves had no power or status. They had no right to a family of their own, could not own property, and had no legal or political rights. The Greek philosopher Aristotle referred to them as “living tools,” and no free Greek is known to have ever advocated the abolition of slavery. By 600 Bc chattel slavery (treating slaves as property) had become widespread in Greece. By the 5th century Bc slaves accounted for as much as one-third of the total population in some city-states. People became slaves after being captured in war or seized by raiders, who then sold them. Children born to slaves became slaves themselves. Greeks took many slaves from non-Greek populations, but they also enslaved other Greeks in war. Greek slaves outside Sparta almost never revolted on a large scale because they were of too many different nationalities and too scattered to organize.

Most families owned slaves as household servants and labourers; even relatively poor people might own one or two slaves. Owners could beat and kill their slaves without penalties. However, hurting good workers made no economic sense because the master would be harming part of his property. To encourage slaves to work hard, owners sometimes promised freedom at a future date. Unlike in Rome, freed slaves in Greece did not become citizens. Instead, former slaves mixed into the population of metics - non-citizens, including people from foreign lands or other states, officially allowed to live in a city-state.

City-states and gods also legally owned slaves (the gods’ slaves were generally managed by the gods’ earthly intermediaries, temple priests). These public slaves enjoyed a measure of independence, living on their own and performing specialized tasks. In Athens, for example, public slaves were trained to look for counterfeit coinage. Temple slaves worked as servants of the sanctuary’s deity. Sparta had a special category of slaves called helots, Greek war captives owned by the state but assigned to Spartan families. Helots raised food and performed household chores so that Spartan women could devote their time to raising strong children and men could devote their time to training as hoplite warriors. The helots lived harsh lives and often revolted. Spartans annually sent out a secret band of young men to murder any helots who looked likely to provoke rebellion.

The figures on this amphora represent participants in a foot race at the Panathenaic Games. City-state festivals provided the most exciting entertainment in ancient Greece. At these gatherings Greeks honoured the gods with competitions in sports, music, dance, drama, and poetry.

The way of life in Greek city-states remained mostly the same for a long time. People in the urban centre lived in low apartment buildings or single-family homes, depending on their wealth. Dwellings, public buildings, and temples were situated around the agora, where people gathered for conversation and to buy food and crafts at daily markets. Citizens also lived in small villages or farmhouses scattered around the city-state’s countryside. In Athens, more people lived outside the city’s wall than inside.

Houses were simple, containing bedrooms, storage rooms, and a kitchen around a small inner courtyard, but no bathrooms. Waste was dumped in a pit outside the door and then collected for disposal in the countryside. Most families were nuclear, meaning a household consisted of a single set of parents and their children, but generally no other relatives. Fathers were responsible for supporting the family by work or by investments in land and commerce. Mothers were responsible for managing the household’s supplies and overseeing the slaves, who fetched water in jugs from public fountains, cooked, cleaned, and looked after babies. Fathers kept a separate room for entertaining guests, because male visitors were not permitted in rooms where women and children spent most of their time. Wealthy men would frequently have friends over for a symposium, a dinner and drinking party. Light came from olive oil lamps, heat from smoky charcoal braziers. Furniture was simple and sparse, usually consisting of wooden chairs, tables, and beds.

Food was simple, too. The poor mainly ate barley porridge flavoured with onions, vegetables, and a bit of cheese or olive oil. Few people ate meat regularly, except for the free distributions of roasted pieces from animal sacrifices at state festivals. Bakeries sold fresh bread daily, and small stands offered snacks. Wine diluted with water was the favourite beverage.

The style of Greek clothing changed little over time. Men and women both wore loose tunics, of somewhat different shapes to fit their body types. The tunics often had colourful designs and were worn cinched with a belt. In cold weather, people wore cloaks and hats, and leather boots replaced the sandals worn in warm temperatures. Women wore jewelry and cosmetics, especially powdered lead to give themselves a pale complexion. Men sported beards until Alexander the Great started a vogue for shaving.

Medicine was limited. Hippocrates, the most famous physician of ancient times, helped separate superstition from medical treatment in the 5th century Bc. Doctors knew of herbal remedies to treat injuries and reduce pain, and they could do some surgery. But they had no cures for infections, and even well-conditioned people could die quickly from disease at any age.

Men kept fit by exercising daily to be ready for military service. Before mercenaries became common in the Hellenistic period, Greek armies consisted of citizen militias manned by ordinary citizens. Every city-state had at least one gymnasium, a combination exercise building, running track, bathing facility, lecture hall, and park, open only to males. Men who lived in the city went there for physical training, ball games, gambling, and relaxation. Women entertained themselves by visiting friends and attending public festivals.

City-state festivals provided the most exciting entertainment. Gods were honoured with competitions in music, dance, drama, and poetry. Athens boasted of holding a festival nearly every other day. The huge Panhellenic festivals held at Olympia, Delphi, Nemea, and Isthmia attracted spectators and professional contestants from throughout the Greek world. Athletes and musicians who won competitions became rich and famous. The most spectacular and expensive competition was chariot racing, which required excellent horses.

Although only men had the right to participate in city-state politics, women were citizens legally, socially, and religiously. Female citizens could own property and could go to court over property disputes. Nonetheless, ancient Greek society was paternalistic, with men acting as “fathers” to regulate the lives of women and safeguard their interests (as defined by men). All women were expected to have male guardians to protect them physically and legally. Women's important religious duties included control over cults reserved exclusively for them and paid service as publicly supported priestesses. Teenage women generally married men in their 20's.

Sparta had a distinctive way of life designed to produce a vigorous military. There, young women could exercise in the open so they could become strong and bear healthy children. Boys left home at age seven to live in public barracks and to begin about 12 years of rigorous physical and moral training under the strict guidance of older men. To make them tough, boys were sometimes required to steal food if they wanted to eat, but they were beaten if they got caught. They were never allowed to talk back, even in the face of humiliating insults and jokes at their expense. When they married, they were not allowed to live with their brides until they turned 30. Any boy who failed the training lost his political rights and endured constant public humiliation.

Traditional Greek religion was pagan polytheism, meaning that it included many gods and other supernatural beings. Greeks inherited many of their ideas about the gods from the Middle East. Their basic belief remained constant: People must honour the gods to thank them for blessings received and to receive blessings in return.

Greeks considered the gods human-like in form and emotions. The gods did not love all human beings; rather, they protected and benefited people and states who paid them honour and avoided offending them. People pleased the gods by sacrificing animals and other foods, decorating their sanctuaries with art, offering prayers, and holding festivals. The gods became angry when people performed sacrifices improperly, violated the sanctity of a temple, or broke their sworn word. Greeks believed that angry gods inflicted punishments such as famine, earthquake, epidemics, or defeat in war.

Greeks also believed that the vast difference in power between people and gods made the divinities’ natures and purposes hard to understand, but traditional stories about the gods provided hints. Some people did not believe all the mythological tales of monsters and divine love affairs with mortals, but everyone respected the myths as lessons about the gods’ awesome might, their inscrutability, and the precariousness of human life. For more direct information people could go to oracles, temples where the gods were believed to answer questions or deliver cures by various means. The priests at an oracle relayed a god’s message, or the visitor could gain clues in a dream as to what the gods wanted. Seers at oracles told prophecies about the future. Pilgrims from beyond the Greek city-states flocked to major oracles, such as at Delphi, to ask for divine advice about marriage, children, money matters, and even foreign policy. The responses were always riddles, because gods were too complex to reply clearly to mere human beings.

As Greek religion evolved, 12 gods emerged as the most important. These gods were believed to assemble for banquets atop Mount Olympus, Greece’s highest peak. Their leader was Zeus, god of the sky. The other gods were Hera, Zeus’s wife and the goddess of marriage; Aphrodite, signifies the goddess of love; Apollo, was the god of the sun; Ares, was the god of war; Artemis, portrayed the goddess of nature; Athena, goddess of wisdom and war. As Demeter, as she was the goddess of grain and the harvest; Dionysus, held to the divinities in and of the god of wine and vegetation; Hephaestus, brought aflame as he was to assemble a the god of fire; Hermes, messenger of the gods; and Poseidon, god of the sea.

City-states built temples to honour the gods protecting their territory and people. Both Athens and Sparta honoured Athena, but with different rituals and prayers. A temple was a house for a god and was not open to worshippers. Only priests and priestesses entered to take care of the god’s statue. The priests and priestesses were guardians only of ritual, not of correct religious thinking. Greek religion had no scripture or uniform set of beliefs and practices. Sacrifices of foods and animals, the main public religious activity, took place outside the front of the temple, where worshippers could gather to affirm their community’s ties to the divine.

Greek religion also had a personal aspect. Particularly important to individuals were so-called mystery cults. Through initiation into special knowledge provided by a god, worshippers could hope for protection in everyday life and a better chance of happiness in the afterlife. Otherwise, the dead could expect only miserable nothingness. The mystery cult of Demeter and her daughter Persephone, headquartered in the Athenian suburb of Eleusis, attracted initiates from all parts of the Greek-speaking world Initiates had to purify themselves of wrongdoing to win entry. This religious emphasis on right conduct became more pronounced in the Hellenistic period as eastern cults, such as that of the Egyptian goddess Isis, won Greek converts.

Christianity took roots among Greeks after emerging from Palestine in the 1st century ad. The New Testament of the Bible was written in Greek, as was a great deal of later Christian literature. Since Christians frequently disagreed with one another about doctrine and ritual, the Byzantine emperors continually tried to enforce uniformity on believers, sometimes by force. The Hellenistic eastern church in Constantinople also developed bitter disputes with the popes in Rome, culminating in the Great Schism, the division of the Orthodox Church from the Roman Catholic Church in 1054.

Except at Sparta, education remained private for most of Greek history. During the Hellenistic period, another city-states established public schools. Only wealthy families could afford to pay teachers. Their sons learned to read, write, and quote famous literature. They were taught to sing or play a musical instrument, and they trained for athletics and military service. Greek sons were studying not for jobs but to become effective citizens. Daughters of wealthy families learned to read, write, and do simple arithmetic so they could manage a household, but they rarely received education past childhood.

A small number of boys continued school beyond childhood. As teenagers, they studied philosophy as a guide to living a moral life, and rhetoric as a tool for making persuasive speeches in court and the political assembly. Especially in democracies of the Classical period, this training in persuasive public speaking was crucial for an ambitious young man. The better speeches a man gave, the more influence and status he could attain. A significant part of a wealthy teenager’s education involved a mentor relationship with an elder. The boy learned by observing his mentor talking politics in the agora, helping him perform his public duties, working out with him in a gymnasium, and attending symposia with him. Sometimes this led to an intimate physical relationship, which was socially acceptable in some city-states but not in others. The richest pupils continued their education at a university in a large city. These universities were organized by famous teachers. Athens had the best universities, including the Lyceum and the Academy.

Poorer children received no formal education. They learned a trade to help support their families and might learn to read and do some mathematics from their parents, enough to help them work as carpenters, stone masons, or merchants. Most poor people were illiterate, unable to do much more than sign their names. Difficulty in reading did not stop people from getting information. They would find someone to read aloud any writing they needed to understand. Greeks were very comfortable absorbing information by ear; even literate people usually read out loud. Greeks were very fond of songs, poems, speeches, stories, plays, and lively conversation, all of which formed part of an informal education.

The Erechtheum is an Ionic temple on Athens’ Acropolis north of the Parthenon. Challenged by uneven ground and by the fear of destroying former religious sanctuaries, the architect was forced to construct it with a complicated asymmetrical floor plan. The entablature, or top, of the porch is supported by six statues of maidens, called caryatids, instead of by columns. Sculptures from the Erechtheum, the Parthenon, and other buildings of ancient Athens are preserved as the Elgin Marbles in the British Museum in London.

Applying enormous creativity to the inspiration that they took from Egypt and the Middle East, Greek thinkers, artists, and authors produced brilliant works that remain famous to this day. Above all, Greeks were curious and open to innovation, so long as it did not threaten to anger the gods or cause social unrest. Artists in vase painting and sculpture and authors of literature introduced fascinating changes to traditional models.

Philosophy and science developed because the most powerful Greek thinkers were sceptical about appearances, insisting that hard work was needed to discover the underlying reasons for things in nature and people's real motives. They also thought there was beauty in the search for truth, whether moral or scientific. This belief encouraged them to persevere despite difficulties. Scientific investigation, for example, was limited by a lack of technology. Scientists and doctors could only wonder about things too small to see with the naked eye, and they could not do experiments that required measurements of very small amounts of time or distance. Therefore, they had no choice but to make ideas and theory more important than practical applications.

The first Greek philosophers were interested in theoretical science. They lived in the Ionia region of western Asia Minor and learned from earlier Middle Eastern thinkers, especially those from Babylonia. The Greek philosophers Thales and Anaximander, who lived in the 6th century Bc, reached the revolutionary conclusion that the physical world was governed by laws of nature, not by the whims of the gods. Pythagoras, who also lived in the 6th century Bc, taught that numbers explained the world and started the study of mathematics in Greece. These philosophers called the universe cosmos, meaning “a beautiful thing,” because it had order based on scientific rules, not mythology. Therefore, the philosophers believed in logic. Their insistence that people produce evidence for their beliefs opened the way to modern science and philosophy.

Philosophers called Sophists upset many people in the 5th century Bc by teaching relativism, the belief that there is no universal truth or right and wrong. The most famous Sophist was Protagoras, who said, “Man is the measure of all things.” Socrates (469-399 Bc) insisted that the Sophists were wrong and that well-informed people would never do wrong on purpose. His pupil Plato (428-347 Bc) became Greece's most famous philosopher. Plato’s complicated works argued universal truths did exist and that the human soul made the body unimportant. Plato founded an academy in Athens that remained in business until ad 529. His pupil Aristotle (384-322 Bc) turned away from theoretical philosophy to teach about practical ethics, self-control, logic, and science. Alexander the Great (whom Aristotle once tutored) sent him information on plants and animals encountered on the march to India. Aristotle's works became so influential that they determined the course of Western scientific thought until modern times.

Hellenistic philosophers concentrated on ethics, helping people achieve tranquillity in a period of change when things seemed out of their control. In the 3rd century Bc, Epicurus taught that people should not be afraid because everything, including our bodies, consists of microscopic atoms that dissolve painlessly at death. Zeno of Citium, who also lived in the 3rd century Bc, founded Stoicism, which taught that life was ruled by fate but that people should still live morally to be in harmony with nature.

The Golden Age of Greek science came in the Hellenistic period, with the greatest advances in mathematics. The geometry theories published by Euclid about 300 Bc still endure. Archimedes (287-212 Bc) calculated the value of pi (the ratio of the circumference of a circle to its diameter) and invented fluid mechanics. Aristarchus, early in the 3rd century Bc, argued that the earth revolved around the sun, while Eratosthenes accurately calculated the circumference of the earth. Also in the 3rd century Bc, Ctesibius invented machines operated by air and water pressure; Hero later built a rotating sphere powered by steam. These inventions did not lead to practical uses because the technology did not yet exist to produce the pipes, fittings, and screws needed to build powerful machines. Military technology vaulted ahead with the invention of huge catapults and wheeled towers to batter down city walls. Finally, medical scientists made many discoveries, such as the significance of the pulse and the nervous system.

The temple of Athena Nike is part of the Acropolis in the city of Athens in Greece. Built around 420 Bc, it is an excellent example of a classical temple, with ionic columns and a frieze around the top.

Greek sculpture and architecture originally followed Egyptian and Middle Eastern models. Statues of the Archaic Period stood stiffly, staring forward, and temples were rectangular boxes on platforms with columns. Later architecture retained this basic plan, although buildings became much bigger. The style of sculpture and pottery, however, changed dramatically over time.

Sculpture was always painted in bright colours, but over time its poses became more lively and lifelike. By the Classical period, Greeks were carving statues in motion and in more relaxed stances. Their spirited movement and calm expressions suggested the era's confident energy. Statues of gods could be 12 m (40 ft) high and covered with gold and ivory, such as Phidias's Athena in the Parthenon temple at Athens. The female nude became popular. Praxiteles's naked Aphrodite of Cnidus became so renowned that the king of Bithynia offered to pay off the city's entire public debt if he could have the statue. Cnidus refused.

Hellenistic artists began showing emotion in their statues. A 3rd-century Bc sculpture from Pergamum showed a defeated Gaul escaping slavery by stabbing himself after having killed his wife. New subjects departed from traditional notions of beauty by representing drunkards, battered boxers, and elderly people with wrinkles.

Greeks painted pottery and turned an everyday item into art. Mycenaean vases featured lively designs of sea creatures and dizzying whorls. Dark Age potters stopped drawing animals, using only geometric patterns. Artists of the Archaic Age, inspired by Middle Eastern pots, reintroduced beasts and people on Greek vases. From then on, vase painters portrayed mythological and everyday scenes with increasing realism. When they switched in the late 6th century Bc from black on red painting to red on black, they could add tiny details that made their pictures come alive.

Greek large-scale architecture began with the Minoan and Mycenaean palaces. These multistory buildings had many rooms entered around courtyards. Balconies provided space for viewing festivals in the open areas below. Architects in the later city-states designed public structures, such as stoas, government buildings, and temples. Stoas were sheltered walkways placed around the agora to provide shade for conversation. Temples were the largest buildings in the city-state. Athens's Parthenon became Greece's most famous building for its size, many columns, and elaborate sculptural decoration. Hellenistic kings outdid the Athenians by erecting huge temples. The temple of Artemis at Ephesus is one of the Seven Wonders of the World.

Greek literature began in the Mycenaean Period as stories told aloud. Mycenaeans used their pictorial script (Linear B) only for the accounting. Fighting from 1200 to 1000 Bc destroyed Greek knowledge of writing, until they adopted an alphabet from Phoenicia in the 8th century Bc to record the exciting poetry of Homer. His epics The Iliad and The Odyssey became Greece's most famous literature. The epics told about the Trojan War and the suffering it caused its heroes and its victims. People loved the stories for their fabulous descriptions of action and for their lessons about the effects of anger and mercy. Hesiod, a poet of the 8th century Bc, also became a lasting favourite with his long stories of how the world began and how justice was the proper guide for life in business and farming. Somewhat later, lyric poets spun short tales of passion and emotion that people loved to sing.

Great literary innovations in drama were produced in Athens in the 5th century Bc. Aeschylus, Sophocles, and Euripides were the most famous authors of tragedies. They based their plays on myths that presented moral issues, especially the danger of hubris (arrogant overconfidence). Theirs colluding infractions were often involved fierce conflicts in families or dangerous interactions between gods and humans. The story of Oedipus, who unknowingly killed his father and married his mother, was one of the most famous tragedies. Plays were performed outdoors at festivals honouring the god Dionysus in a competition sponsored by the city-state. Thousands of people packed the theatre. Each author presented three tragedies, followed by a semicomic play featuring satyrs (mythical half-man, half-animal beings). Actors wore colourful costumes and masks; a chorus danced and sang as part of each play.

Comedies also were performed in these competitions. These plays displayed remarkable freedom of speech in criticizing public policy and making fun of politicians. There plots could be fantastic, for example having a character fly up on a dung beetle to ask the gods for peace. Their language featured jokes, puns, and obscenities. The most famous comic playwright was Aristophanes, who wrote some comedies with powerful women as main characters. Greek comedy in the 4th century Bc changed from political commentary to social satire. Authors such as Menander produced comedies that provided insights into human weaknesses and the complications of everyday life.

Greeks began writing about history in the 5th century Bc. Herodotus and Thucydides wrote long works that stressed eyewitness evidence, the multiple causes of events, and judgments about people's motives. Thucydides, followed by Aristotle, developed political science by analysing how states operated. Hellenistic Greek writers made history more personal and began composing biographies.

The enduring legacy of ancient Greece lies in the brilliance of its ideas and the depth of its literature and art. The greatest ancient evidence of their value is that the Romans, who conquered the Greeks in war, were themselves overcome by admiration for Greek cultural achievements. The first Roman literature, for example, was Homer's Odyssey translated into Latin. Greek art, architecture, philosophy, and religion also inspired Roman artists and thinkers, who used them as starting points for developing their own style of work. All educated Romans learned to read and speak Greek and studied Greek models in rhetoric. Stoicism became the most popular Roman philosophy of life.

Arab philosophers, mathematicians, and scientists who became the leading thinkers of medieval times studied the works of Aristotle and other Greek sources intensely. During the European Renaissance from the 14th to the 16th centuries, people from many walks of life read Greek literature and history. Writing in the late 16th and early 17th centuries, English playwright William Shakespeare based dramas on ancient Greek biographies. Modern playwrights still find inspiration for new works in Athenian drama. Many modern public buildings, such as the United States Supreme Court in Washington, DC, imitate Greek temple architecture. Although the founders of the United States rejected Athenian democracy as too direct and radical, they enshrined democratic equality as a basic principle. It was ancient Greeks who proved that democracy could be the foundation of a stable government. Pride in the cultural accomplishments of ancient Greece contributed to a feeling of ethnic unity when the modern nation of Greece was carved out of the Ottoman Empire. That pride still characterizes modern Greece and makes it a fierce defender of the Hellenic heritage.

Reliance on logic, allegiance to democratic principles, unceasing curiosity about what lies beneath the surface of things, some healthy respects for the dangers of arrogant overconfidence, and a love of beauty in stories and art remain incredibly important components of Western civilization. Ancient Greece contributed all of these things.

Philosophy is a rational and critical inquiry into basic principles. Philosophy is often divided into four main branches: Metaphysics, the investigation of an ultimate reality, as epistemology, the study of the origins, validity, and limits of knowledge; ethics is concerned with studying the nature of morality and judgment; and aesthetics, the study of the nature of beauty in the fine arts.

The School of Athens (1510-1511) by Italian Renaissance painter Raphael adorns a room in the Vatican Palace. The artist depicts several philosophers of classical antiquity and portrays each with a distinctive gesture, conveying complex ideas in simple images. In the centre of the composition, Plato and Aristotle dominate the scene. Plato points upward to the world of ideas, where he believes knowledge lies, whereas Aristotle holds his forearm parallel to the earth, stressing observation of the world around us as the source of understanding. In addition, Raphael draws comparisons with his illustrious contemporaries, giving Plato the face of the Renaissance genius Leonardo da Vinci, and Heraclitus, who rests his elbow on a large marble block, the face of the Renaissance sculptor Michelangelo. Euclid, bending down at the right, resembles the Renaissance architect Bramante. Raphael paints his own portrait on the young man in a black beret at the far right. In accordance with Renaissance ideas, artists belong to the ranks of the learned and the fine arts have the stature and merit of the written word.

As used originally by the ancient Greeks, the term philosophy meant the pursuit of knowledge for its own sake. Philosophy comprised all areas of speculative thought and included the arts, sciences, and religion. As special methods and principles were developed in the various areas of knowledge, each area acquired its own philosophical aspect, giving rise to the philosophy of art, of science, and of religion. The term philosophy is often used popularly to mean a set of basic values and attitudes toward life, nature, and society—thus the phrase “philosophy of life.” Because the lines of distinction between the various areas of knowledge are flexible and subject to change, the definition of the term philosophy remains a subject of controversy.

Western philosophy from Greek antiquity to the present is surveyed in the remainder of this article. For information about philosophical thought in Asia and the Middle East,

Western philosophy is generally considered to have begun in ancient Greece as speculation about the underlying nature of the physical world. In its earliest form, it was indistinguishable from natural science. The writings of the earliest philosophers no longer exist, except for a few fragments cited by Aristotle in the 4th century Bc and by other writers of later times.

The first philosopher of historical record was Thales, who lived in the 6th century Bc in Miletus, a metropolis on the Ionian coast of Asia Minor. Thales, who was revered by later generations as one of the Seven Wise Men of Greece, was interested in astronomical, physical, and meteorological phenomena. His scientific investigations led him to speculate that all natural phenomena are different forms of one fundamental substance, which he believed to be water because he thought evaporation and condensation to be universal processes. Anaximander, a disciple of Thales, maintained that the first principle from which all things evolve is an intangible, invisible, infinite substance that he called apeiron, “the boundless.” This substance, he maintained, is eternal and indestructible. Out of its ceaseless motion the more familiar substances, such as warmth, cold, earth, air, and fire, continuously evolve, generating in turn the various objects and organisms that make up the recognizable world.

The third great Ionian philosopher of the 6th century Bc, Anaximenes, returned to Thales’s assumption that the primary substance is something familiar and material, but he claimed it to be air rather than water. He believed that the changes things undergo could be explained in terms of rarefaction (thinning) and condensation of air. Thus Anaximenes was the first philosopher to explain differences in quality in terms of differences in size or quantity, a method fundamental to physical science.

Overall, the Ionian school made the initial radical step from mythological to scientific explanation of natural phenomena. It discovered the important scientific principles of the permanence of substance, the natural evolution of the world, and the reduction of quality to quantity.

The 6th-century-Bc Greek mathematician and philosopher Pythagoras was not only an influential thinker, but also a complex personality whose doctrines addressed the spiritual as well as the scientific. The following is a collection of short excerpts from studies of Pythagorean teachings and from anecdotes about Pythagoras written by later Greek thinkers, such as the philosopher Aristotle, the historian’s Herodotus and Diodorus Siculus, and the biographer Diogenes Laërtius.

About 530 Bc at Croton (now Crotona), in southern Italy, the philosopher Pythagoras founded a school of philosophy that was more religious and mystical than the Ionian school. It fused the ancient mythological view of the world with the developing interest in scientific explanation. The system of philosophy that became known as Pythagoreanism combined ethical, supernatural, and mathematical beliefs with many ascetic rules, such as obedience and silence and simplicity of dress and possessions. The Pythagoreans taught and practiced a way of life based on the belief that the soul is a prisoner of the body, is released from the body at death, and migrates into a succession of different kinds of animals before reincarnation into a human being. For this reason Pythagoras taught his followers not to eat meat. Pythagoras maintained that the highest purpose of humans should be to purify their souls by cultivating intellectual virtues, refraining from sensual pleasures, and practising special religious rituals. The Pythagoreans, having discovered the mathematical laws of musical pitch, inferred that planetary motions produce a “music of the spheres,” and developed a “therapy through music” to bring humanity in harmony with the celestial spheres. They identified science with mathematics, maintaining that all things are made up of numbers and geometrical figures. They made important contributions to mathematics, musical theory, and astronomy.

Heraclitus of Ephesus, who was active around 500 Bc, continued the search of the Ionians for a primary substance, which he claimed to be fire. He noticed that heat produces changes in matter, and thus anticipated the modern theory of energy. Heraclitus maintained that all things are in a state of continuous flux, that stability is an illusion, and that only change and the law of change, or Logos, are real. The Logos doctrine of Heraclitus, which identified the laws of nature with a divine mind, developed into the pantheistic theology of Stoicism. (Pantheism is the belief that God and material substance are one, and that divinity is present in all things.)

In the 5th century Bc, Parmenides founded a school of philosophy at Elea, a Greek colony on the Italian peninsula. Parmenides took a position opposite from that of Heraclitus on the relation between stability and change. Parmenides maintained that the universe, or the state of being, is an indivisible, unchanging, spherical entity and that all reference to change or diversity is self-contradictory. According to Parmenides, all that exists has no beginning and has no end and is not subject to change over time. Nothing, he claimed, can be truly asserted except that “being is.” Zeno of Elea, a disciple of Parmenides, tried to prove the unity of being by arguing that the belief in the reality of change, diversity, and motion leads to logical paradoxes. The paradoxes of Zeno became famous intellectual puzzles that philosophers and logicians of all subsequent ages have tried to solve. The concern of the Eleatics with the problem of logical consistency laid the basis for the development of the science of logic.

The speculation about the physical world begun by the Ionians was continued in the 5th century Bc by Empedocles and Anaxagoras, who developed a philosophy replacing the Ionian assumption of a single primary substance with an assumption of a plurality of such substances. Empedocles maintained that all things are composed of four irreducible elements: air, water, earth, and fire, which are alternately combined and separated by two opposite forces, love and strife. By that process the world evolves from chaos to form and back to chaos again, in an eternal cycle. Empedocles regarded the eternal cycle as the proper object of religious worship and criticized the popular belief in personal deities, but he failed to explain the way in which the familiar objects of experience could develop out of elements that are totally different from them. Anaxagoras therefore suggested that all things are composed of very small particles, or “seeds,” which exist in infinite variety. To explain the way in which these particles combine to form the objects that constitute the familiar world, Anaxagoras developed a theory of cosmic evolution. He maintained that the active principle of this evolutionary process is a world mind that separates and combines the particles. His concept of elemental particles led to the development of an atomic theory of matter.

It was a natural step from pluralism to atomism, the theory that all matter is composed of tiny, indivisible particles differing only in simple physical properties such as size, shape, and weight. This step was taken in the 4th century Bc by Leucippus and his more famous associate Democritus, who is generally credited with the first systematic formulation of an atomic theory of matter. The fundamental assumption of Democritus’s atomic theory is that matter is not too divisible but is composed of numerous indivisible particles that are too small for human senses to detect. His conception of nature was thoroughly materialistic (focussed on physical aspects of matter), explaining all natural phenomena in terms of the number, shape, and size of atoms. He thus reduced the sensory qualities of things, such as warmth, cold, taste, and odour, to quantitative differences among atoms - that is, to differences measurable in amount or size. The higher forms of existence, such as plant and animal life and even human thought, were explained by Democritus in these purely physical terms. He applied his theory to psychology, physiology, theory of knowledge, ethics, and politics, thus presenting the first comprehensive statement of deterministic materialism, a theory claiming that all aspects of existence rigidly follow, or are determined by, physical laws.

Toward the end of the 5th century Bc, a group of travelling teachers called Sophists became famous throughout Greece. The Sophists played an important role in developing the Greek city-states from agrarian monarchies into commercial democracies. As Greek industry and commerce expanded, a class of newly rich, economically powerful merchants began to wield political power. Lacking the education of the aristocrats, they sought to prepare themselves for politics and commerce by paying the Sophists for instruction in public speaking, legal argument, and general culture. Although the best of the Sophists made valuable contributions to Greek thought, the group as a whole acquired a reputation for deceit, insincerity, and demagoguery. Thus the word sophistry has come to signify these moral faults.

The famous maxim of Protagoras, one of the leading Sophists, that “man is the measure of all things,” is typical of the philosophical attitude of the Sophist school. Protagoras claimed that individuals have the right to judge all matters for themselves. He denied the existence of an objective (demonstrable and impartial) knowledge, arguing instead that truth is subjective in the sense that different things are true for different people and there is no way to prove that one person’s beliefs are objectively correct and another’s are incorrect. Protagoras asserted that natural science and theology are of little or no value because they have no impact on daily life, and he concluded that ethical rules need be followed only when it is to one’s practical advantage to do so.

Socrates was a Greek philosopher and teacher who lived in Athens, Greece, in the 400s Bc. He profoundly altered Western philosophical thought through his influence on his most famous pupil, Plato, who passed on Socrates’s teachings in his writings known as dialogues. Socrates taught that every person has full knowledge of ultimate truth contained within the soul and needs only to be spurred to conscious reflection in order to become aware of it. His criticism of injustice in Athenian society led to his prosecution and a death sentence for allegedly corrupting the youth of Athens.

Perhaps the greatest philosophical personality in history was Socrates, who lived from 469 to 399 Bc. Socrates left no written work and is known through the writings of his students, especially those of his most famous pupil, Plato. Socrates maintained a philosophical dialogue with his students until he was condemned to death and took his own life. Unlike the Sophists, Socrates refused to accept payment for his teachings, maintaining that he had no positive knowledge to offer except the awareness of the need for more knowledge. He concluded that, in matters of morality, it is best to seek out genuine knowledge by exposing false pretensions. Ignorance is the only source of evil, he argued, so it is improper to act out of ignorance or to accept moral instruction from those who have not proven their own wisdom. Instead of relying blindly on authority, we should unceasingly question our own beliefs and the beliefs of others in order to seek out genuine wisdom.

Greek philosopher Socrates chose to die rather than cease teaching his philosophy, declaring that “no evil can happen to a good man, either in life or after death.” In 399 Bc Socrates was accused and convicted of impiety and moral corruption of the youth of Athens, Greece. At his trial, he presented a justification of his life. The substance of his speech was recorded by Greek philosopher Plato, a disciple of Socrates, in Plato’s Apology.

Socrates taught that every person has full knowledge of ultimate truth contained within the soul and needs only to be spurred to conscious reflection to become aware of it. In Plato’s dialogue Meno, for example, Socrates guides an untutored slave to the formulation of the Pythagorean theorem, thus demonstrating that such knowledge is innate in the soul, rather than learned from experience. The philosopher’s task, Socrates believed, was to provoke people into thinking for themselves, rather than to teach them anything they did not already know. His contribution to the history of thought was not a systematic doctrine but a method of thinking and a way of life. He stressed the need for analytical examination of the grounds of one’s beliefs, for clear definitions of basic concepts, and for a rational and critical approach to ethical problems.

Plato, one of the most famous philosophers of ancient Greece, was the first to use the term philosophy, which means “love of knowledge.” Born around 428 Bc, Plato investigated a wide range of topics. Chief among his ideas was the theory of forms, which proposed that objects in the physical world merely resemble perfect forms in the ideal world, and that only these perfect forms can be the object of true knowledge. The goal of the philosopher, according to Plato, is to know the perfect forms and to instruct others in that knowledge.

Plato, who lived from about 428 to 347 Bc, was a more systematic and positive thinker than Socrates, but his writings, particularly the earlier dialogues, can be regarded as a continuation and elaboration of Socratic insights. Like Socrates, Plato regarded ethics as the highest branch of knowledge; he stressed the intellectual basis of virtue, identifying virtue with wisdom. This view led to the so-called Socratic paradox that, as Socrates asserts in the Protagoras, “no man does evil voluntarily.” (Aristotle later noticed that such a conclusion allows no place for moral responsibility.) Plato also explored the fundamental problems of natural science, political theory, metaphysics, theology, and theory of knowledge, and developed ideas that became permanent elements in Western thought.

Many experts believe that philosophy as an intellectual discipline originated with the work of Plato, one of the most celebrated philosophers in history. The Greek thinker had an immeasurable influence on Western thought. However, Plato’s expression of ideas in the form of dialogues—the dialectical method, used most famously by his teacher Socrates—has led to difficulties in interpreting some of the finer points of his thoughts. The issue of what exactly Plato meant to say is addressed in the following excerpt by author R. M. Hare.

The basis of Plato’s philosophy is his theory of Ideas, also known as the doctrine of Forms. The theory of Ideas, which is expressed in many of his dialogues, particularly the Republic and the Parmenides, divides existence into two realms, an “intelligible realm” of perfect, eternal, and invisible Ideas, or Forms, and a “sensible realm” of concrete, familiar objects. Trees, stones, human bodies, and other objects that can be known through the senses are for Plato unreal, shadowy, and imperfect copies of the Ideas of tree, stone, and the human body. He was led to this apparently bizarre conclusion by his high standard of knowledge, which required that all genuine objects of knowledge be described without contradiction. Because all objects perceived by the senses undergo change, an assertion made about such objects at one time will not be true at a later time. According to Plato, these objects are therefore not completely real. Thus, beliefs derived from experience of such objects are vague and unreliable, whereas the principles of mathematics and philosophy, discovered by inner meditation on the Ideas, constitute the only knowledge worthy of the name. In the Republic, Plato described humanity as imprisoned in a cave and mistaking shadows on the wall for reality; he regarded the philosopher as the person who penetrates the world outside the cave of ignorance and achieves a vision of the true reality, the realm of Ideas. Plato’s concept of the Absolute Idea of the Good, which is the highest Form and includes all others, has been a main source of pantheistic and mystical religious doctrines in Western culture.

What is the nature of knowledge? And of ignorance? The 4th-century-Bc Greek philosopher Plato used the myth, or allegory, of the cave to illustrate the difference between genuine knowledge and opinion or belief. This distinction is at the heart of one of Plato’s most important works, The Republic. In the first part of the myth of the cave, excerpted here, Plato constructs a dialogue in which he considers the difficult transition from belief based on appearances to true understanding founded in reality.

Plato’s theory of Ideas and his rationalistic view of knowledge formed the foundation for his ethical and social idealism. The realm of eternal Ideas provides the standards or ideals according to which all objects and actions should be judged. The philosophical person, who refrains from sensual pleasures and searches instead for knowledge of abstract principles, finds in these ideals the basis for personal behaviour and social institutions. Personal virtue consists in a harmonious relation among the three parts of the soul: reason, emotion, and desire. Social justice likewise consists in harmony among the classes of society. The ideal state of a sound mind in a sound body requires that the intellect control the desires and passions, as the ideal state of society requires that the wisest individuals rule the pleasure-seeking masses. Truth, beauty, and justice coincide in the Idea of the Good, according to Plato; therefore, art that expresses moral values is the best art. In his rather conservative social program, Plato supported the censorship of art forms that he believed corrupted the young and promoted social injustice.

A student of ancient Greek philosopher Plato, Aristotle shared his teacher’s reverence for human knowledge but revised many of Plato’s ideas by emphasizing methods rooted in observation and experience. Aristotle surveyed and systematized nearly all the extant branches of knowledge and provided the first ordered accounts of biology, psychology, physics, and literary theory. In addition, Aristotle invented the field known as formal logic, pioneered zoology, and addressed virtually every major philosophical problem known during his time. Known to medieval intellectuals as simply “the Philosopher,” Aristotle is possibly the greatest thinker in Western history and, historically, perhaps the single greatest influence on Western intellectual development.

Aristotle, who began study at Plato’s Academy at age 17 in 367 Bc, was the most illustrious pupil of Plato, and ranks with his teacher among the most profound and influential thinkers of the Western world. After studying for many years at Plato’s Academy, Aristotle had in becoming the tutor of Alexander the Great. He later returned to Athens to found the Lyceum, a school that, like Plato’s Academy, remained for centuries one of the great centres of learning in Greece. In his lectures at the Lyceum, Aristotle defined the basic concepts and principles of many of the sciences - such as logic, biology, physics, and psychology. In founding the science of logic, he developed the theory of deductive inference - a process for drawing conclusions from accepted premises by means of logical reasoning. His theory is exemplified by the syllogism (a deductive argument having two premises and a conclusion), and a set of rules for scientific method.

In his metaphysical theory, Aristotle criticized Plato’s theory of Forms. Aristotle argued that forms could not exist by themselves but existed only in particular things, which are composed of both form and matter. He understood substances as matter organized by a particular form. Humans, for example, are composed of flesh and blood arranged to shape arms, legs, and the other parts of the body.

Nature, for Aristotle, is an organic system of things whose forms make it possible to arrange them into classes comprising species and genera. Each species, he believed, has a form, purpose, and mode of development in terms of which it can be defined. The aim of science is to define the essential forms, purposes, and modes of development of all species and to arrange them in their natural order in accordance with their complexities of form, the main levels being the inanimate, the vegetative, the animal, and the rational. The soul, for Aristotle, is the form of the body, and humans, whose rational souls are a higher form than the souls of other terrestrial species, are the highest species of perishable things. The heavenly bodies, composed of an imperishable substance, or ether, and moved eternally in perfect circular motion by God, are still higher in the order of nature. This hierarchical classification of nature was adopted by many Christian, Jewish, and Muslim theologians in the Middle Ages as a view of nature consistent with their religious beliefs.

Aristotle’s political and ethical philosophy similarly developed out of a critical examination of Plato’s principles. The standards of personal and social behaviour, according to Aristotle, must be found in the scientific study of the natural tendencies of individuals and societies rather than in a heavenly or abstract realm of pure forms. Less insistent therefore than Plato on a rigorous conformity to absolute principles, Aristotle regarded ethical rules as practical guides to a happy and well-rounded life. His emphasis on happiness, as the active fulfilment of natural capacities, expressed the attitude toward life held by cultivated Greeks of his time. In political theory, Aristotle agreed with Plato that a monarchy ruled by a wise king would be the ideal political structure, but he also recognized that societies differ in their needs and traditions and believed that a limited democracy is usually the best compromise. In his theory of knowledge, Aristotle rejected the Platonic doctrine that knowledge is innate and insisted that it can be acquired only by generalization from experience. He interpreted art as a means of pleasure and intellectual enlightenment rather than an instrument of moral education. His analysis of Greek tragedy has served as a model of literary criticism.

From the 4th century Bc to the rise of Christian philosophy in the 4th century ad, Epicureanism, Stoicism, Skepticism, and Neoplatonism were the main philosophical school in the Western world. Interest in natural science declined steadily during this period, and these schools concerned themselves mainly with ethics and religion. This was also a period of intense intercultural contact, and Western philosophers were influenced by ideas from Buddhism in India, Zoroastrianism in Persia, and Judaism in Palestine.

Greek philosopher Epicurus was a prolific author and creator of an ethical philosophy based upon the achievement of pleasure and happiness. However, he viewed pleasure as the absence of pain and removal of the fear of death. This bust of Epicurus, a Roman copy of a Greek original, is in the Palazzo Nuovo in Rome, Italy.

In 306 Bc Epicurus founded a philosophical school in Athens. Because his followers met in the garden of his home they became known as philosophers of the garden. Epicurus adopted the atomistic physics of Democritus, but he allowed for an element of chance in the physical world by assuming that the atoms sometimes swerve in unpredictable ways, thus providing a physical basis for a belief in free will. The overall aim of Epicurus’s philosophy was to promote happiness by removing the fear of death. He maintained that natural science is important only if it can be applied in making practical decisions that help humans achieve the maximum amount of pleasure, which he identified with gentle motion and the absence of pain. The teachings of Epicurus are preserved mainly in the philosophical poem De Rerum Natura (On the Nature of Things) written by the Roman poet Lucretius in the 1st century Bc. Lucretius contributed greatly to the popularity of Epicureanism in Rome.

Emperor Marcus Aurelius ruled the Roman Empire from 161 to 180. His reign was marked by epidemics and frequent wars along the empire’s frontiers. A champion of the poor, Marcus Aurelius reduced the tax burden while founding schools, hospitals, and orphanages. A Stoic, Marcus Aurelius believed that a moral life leads to tranquillity and that moderation and acceptance improved the quality of one’s life.

The Stoic school, founded in Athens about 310 Bc by Zeno of Citium, developed out of the earlier movement of the Cynics, who rejected social institutions and material (worldly) values. Stoicism became the most influential school of the Greco-Roman world, producing such remarkable writers and personalities as the Greek slave and philosopher Epictetus in the 1st century ad and the 2nd-century Roman emperor Marcus Aurelius, who was noted for his wisdom and nobility of character. The Stoics taught that one can achieve freedom and tranquillity only by becoming insensitive to material comforts and external fortune and by dedicating oneself to a life of virtue and wisdom. They followed Heraclitus in believing the primary substance to be fire and in worshipping the Logos, which they identified with the energy, law, reason, and providence (divine guidance) found throughout nature. The Stoics argued that nature was a system designed by the divinities and believed that humans should strive to live in accordance with nature. The Stoic doctrine that each person is part of God and that all people form a universal family helped break down national, social, and racial barriers and prepare the way for the spread of Christianity. The Stoic doctrine of natural law, which makes human nature the standard for evaluating laws and social institutions, had an important influence on Roman and later Western law.

Roman emperor and philosopher Marcus Aurelius (121-180 ad) recorded principles of Stoic philosophy in his work, Meditations, which is essentially a notebook of jottings, covering a wide range of subjects. These extracts demonstrate the influence of Stoicism, the predominant philosophy of the time with its emphasis on the virtues of wisdom, courage, justice, and temperance, which free the soul from passion and desire.

The school of Skepticism, which continued the Sophist criticisms of objective knowledge, dominated Plato’s Academy in the 3rd century Bc. The Skeptics discovered, as had Zeno of Elea, that logic is a powerful critical device, capable of destroying any positive philosophical view, and they used it skilfully. Their fundamental assumption was that humanity cannot attain knowledge or wisdom concerning reality, and they therefore challenged the claims of scientists and philosophers to investigate the nature of reality. Like Socrates, the Skeptics insisted that wisdom consisted in awareness of the extent of one’s own ignorance. The Skeptics concluded that the way to happiness lies in a complete suspension of judgment. They believed that suspending judgment about the things of which one has no true knowledge creates tranquillity and fulfilment. As an extreme example of this attitude, it is said that Pyrrho, one of the most noted Skeptics, refused to change direction when approaching the edge of a cliff and had to be diverted by his students to save his life.

During the 1st century ad the Jewish-Hellenistic philosopher Philo of Alexandria combined Greek philosophy, particularly Platonic and Pythagorean ideas, with Judaism in a comprehensive system that anticipated Neoplatonism and Jewish, Christian, and Muslim mysticism. Philo insisted that the nature of God so far transcended (surpassed) human understanding and experience as to be indescribable; he described the natural world as a series of stages of descent from God, terminating in matter as the source of evil. He advocated a religious state, or theocracy, and was one of the first to interpret the Old Testament for the Gentiles.

Neoplatonism, one of the most influential philosophical and religious schools and an important rival of Christianity, was founded in the 3rd century ad by Ammonius Saccus and his more famous disciple Plotinus. Plotinus based his ideas on the mystical and poetic writings of Plato, the Pythagoreans, and Philo. The main function of philosophy, for him, is to prepare individuals for the experience of ecstasy, in which they become one with God. God, or the One, is beyond rational understanding and is the source of all reality. The universe emanates from the One by a mysterious process of overflowing of divine energy in successive levels. The highest levels form a trinity of the One; as the Logos, which contains the Platonic Forms; and the World Soul, which gives rise to human souls and natural forces. The farther things emanate from the One, according to Plotinus, the more imperfect and evil they are and the closer they approach the limit of pure matter. The highest goal of life is to purify oneself of dependence on bodily comforts and, through philosophical meditation, to prepare oneself for an ecstatic reunion with the One. Neoplatonism exerted a strong influence on medieval thought.

During the decline of Greco-Roman civilization, Western philosophers turned their attention from the scientific investigation of nature and the search for worldly happiness to the problem of salvation in another and better world. By the 3rd century ad, Christianity had spread to the more educated classes of the Roman Empire. The religious teachings of the Gospels were combined by the Fathers of the Church with many of the philosophical concepts of the Greek and Roman schools. Of particular importance were the First Council of Nicaea in 325 and the Council of Ephesus in 431, which drew upon metaphysical ideas of Aristotle and Plotinus to establish important Christian doctrines about the divinity of Jesus and the nature of the Trinity.

Saint Augustine, born in what is now Souk-Ahras, Algeria, in ad 354, brought a systematic method of philosophy to Christian theology. Augustine taught rhetoric in the ancient cities of Carthage, Rome, and Milan before his Christian baptism in 387. His discussions of the knowledge of truth and of the existence of God drew from the Bible and from the philosophers of ancient Greece. A vigorous advocate of Roman Catholicism, Augustine developed many of his doctrines while attempting to resolve theological conflicts with Donatism and Pelagianism, two heretical Christian movements.

The process of reconciling the Greek emphasis on reason with the emphasis on religious emotion in the teachings of Christ and the apostles found eloquent expression in the writings of Saint Augustine during the late 4th and early 5th centuries. He developed a system of thought that, through subsequent amendments and elaborations, eventually became the authoritative doctrine of Christianity. Largely as a result of his influence, Christian thought was Platonic in spirit until the 13th century, when Aristotelian philosophy became dominant. Augustine argued that religious faith and philosophical understanding are complementary rather than opposed and that one must “believe in order to understand and understand in order to believe.” Like the Neoplatonists, he considered the soul a higher form of existence than the body and taught that knowledge consists in the contemplation of Platonic ideas as abstract notions apart from sensory experience and anything physical or material.

Saint Augustine, an influential theologian and writer in the Western Church, wrote The City of God in the 5th century. In the following excerpt from the final book, or chapter, of this work, Augustine addressed a number of theological issues, including free will and the resurrection of the faithful. He asserted that God did not deprive people of their free will even when they turned to sin because it was preferable to “bring good out of evil than to prevent the evil from coming into existence.” Augustine believed that the human body would rise after death, transformed into “the newness of the spiritual body” and in paradise these new beings would “rest and see, see and love, loving and praise.”

Platonic philosophy was combined with the Christian concept of a personal God who created the world and predestined (determined in advance) its course, and with the doctrine of the fall of humanity, requiring the divine incarnation in Christ. Augustine attempted to provide rational understanding of the relation between divine predestination and human freedom, the existence of evil in a world created by a perfect and all-powerful God, and the nature of the Trinity. Late in his life Augustine came to a pessimistic view about original sin, grace, and predestination: The ultimate fates of humans, he decided, are predetermined by God in the sense that some people are granted divine grace to enter heaven and others are not, and human actions and choices cannot explain the fates of individuals. This view was influential throughout the Middle Ages and became even more important during the Reformation of the 16th century when it inspired the doctrine of predestination put forth by Protestant theologian John Calvin.

Augustine conceived of history as a dramatic struggle between the good in humanity, as 0expressed in loyalty to the “city of God,” or community of saints, and the evil in humanity, as embodied in the earthly city with its material values. His view of human life was pessimistic, asserting that happiness is impossible in the world of the living, where even with good fortune, which is rare, awareness of approaching death would mar any tendency toward satisfaction. He believed further that without the religious virtues of faith, hope, and charity, which require divine grace to be attained, a person cannot develop the natural virtues of courage, justice, temperance, and wisdom. His analyses of time, memory, and inner religious experience have been a source of inspiration for metaphysical and mystical thought.

Saint Augustine, a theologian and scholar of the Roman Catholic Church, did not embrace Christianity until he was more than 30 years old, but soon after his conversion his writings became influential in a number of theological debates. Author Henry Chadwick explores several works by Augustine, including his interpretation of Genesis, the doctrine of the trinity, and his attempts to reconcile biblical views with the prevailing scientific and philosophical views of the time.

The only major contribution to Western philosophy in the three centuries following the death of Augustine in ad 430 was made by the 6th-century Roman statesman Boethius, who revived interest in Greek and Roman philosophy, particularly Aristotle’s logic and metaphysics. In the 9th century the Irish monk John Erigena developed a pantheistic interpretation of Christianity, identifying the divine Trinity with the One, Logos, and World Soul of Neoplatonism and maintaining that both faith and reason are necessary to achieve the ecstatic union with God.

Even more significant for the development of Western philosophy was the early 11th-century Muslim philosopher Avicenna. His work modifying Aristotelian metaphysics introduced a distinction important to later philosophy between essence (the fundamental qualities that make a thing what it is - the tree-ness of a tree, for example) and existence (being, or living reality). He also demonstrated how it is possible to combine the biblical view of God with Aristotle’s philosophical system. Avicenna’s writings on logic, mathematics, physics, and medicine remained influential for centuries.

The 12th-century scholar Peter Abelard was one of the most famous theologians and philosophers of his time. In 1117 he began tutoring Héloïse, the niece of a French cleric. Abelard and Héloïse soon became secret lovers, but were forced to separate after being discovered by Héloïse’s uncle. The two lovers retired to monasteries, and although they kept in touch by writing, they did not see each other again.

In the 11th century a revival of philosophical thought began as a result of the increasing contact between different parts of the Western world and the general reawakening of cultural interests that culminated in the Renaissance. The works of Plato, Aristotle, and other Greek thinkers were translated by Arab scholars and brought to the attention of philosophers in Western Europe. Muslim, Jewish, and Christian philosophers interpreted and clarified these writings in an effort to reconcile philosophy with religious faith and to provide rational grounds for their religious beliefs. Their labours established the foundations of Scholasticism.

Boethius had been a 6th-century Roman philosopher and statesman. He wrote The Consolation of Philosophy (523) while in prison, awaiting execution. The book portrayed philosophy - that is, a system of thought that would sustain Boethius in his tribulations - as a woman. In a dialogue with Boethius, she told him that everyone’s life is transient and filled with problems. But through philosophy, she said, one can achieve serenity despite life’s reversals and misfortunes.

Scholastic thought was less interested in discovering new facts and principles than in demonstrating the truth of existing beliefs. Its method was therefore dialectical (based upon logical argument), and its intense concern with the logic of argument led to important developments in logic as well as theology. The Scholastic philosopher Saint Anselm of Canterbury adopted Augustine’s view of the complementary relation between faith and reason combined accrediting the results to Platonism with Christian theology. Supporting the Platonic theory of Ideas, Anselm argued in favour of the separate existence of universals, or common properties of things - the properties Avicenna had called essences. He thus established the position of logical realism - an assertion that universals and other ideas exist independently of our awareness of them—on one of the most vigorously disputed issues of medieval philosophy.

Regarded as the outstanding Jewish philosopher of the Middle Ages, Maimonides was born in Córdoba, Spain, in 1135. In one of the greatest works of Jewish religious philosophy, Guide for the Perplexed (1190? ; trans. 1881-1885), Maimonides addresses the nature of God and creation, free will, and the dilemma of good and evil. He advocates an allegorical, rather than a literal, interpretation of biblical depictions of God’s nature and actions, a view that was controversial at the time. In the following excerpts from the treatise’s introduction and conclusion, Maimonides explains the purpose of his writing and discusses the intellectual love of God, which he considers the perfect form of worship. Richard S. Sarason

On the contrary view, known as nominalism, was formulated by the Scholastic philosopher Roscelin, who maintained that only individual, solid objects exist and that the universals, forms, and ideas, under which particular things are classified, constitute mere sounds or names, rather than intangible substances. When he argued that the Trinity must consist of three separate beings, his views were deemed heretical and he was forced to recant in 1092. The French Scholastic theologian Peter Abelard, whose tragic love affair with Héloïse in the 12th century is one of the most memorable romantic stories in medieval history, proposed a compromise between realism and nominalism known as conceptualism, according to which universals exist in particular things as properties and outside of things as concepts in the mind. Abelard maintained that revealed religion—religion based on divine revelation, or the word of God—must be justified by reason. He developed his principles as drawn upon the ethics as based on personal conscience that anticipated Protestant thought.

Saint Thomas Aquinas was a leading theologian and philosopher during the so-called golden age of scholasticism in the 13th century. The following passage from his Summa Theologica provides a good example of the scholastic method, which began with a question, then assembled arguments on the question that were eventually reconciled. Aquinas draws upon many authorities for his discussion, ranging from 4th-century Bc Greek philosopher Aristotle to Christian theologian Saint Augustine (ad 354-430)

The Spanish-Arab jurist and physician Averroës, the most noted Muslim philosopher of the Middle Ages, made Aristotelian science and philosophy a powerful influence on medieval thought with his lucid and scholarly commentaries on the works of Aristotle. He earned himself the title “the Commentator” among the many Scholastics who came to regard Aristotle as “the Philosopher.” Averroës attempted to overcome the contradictions between Aristotelian philosophy and revealed religion by distinguishing between two separate systems of truth, a scientific body of truths based on reason and a religious body of truths based on revelation. His view that ‘reason’ takes precedence over religion led to his exile in 1195. Averroës’s so-called double-truth doctrine influenced many Muslim, Jewish, and Christian philosophers; it was rejected, however, by many others, and became an important issue in medieval philosophy.

Thirteenth-century Italian philosopher and theologian Saint Thomas Aquinas attempted to synthesize Christian belief with a broad range of human knowledge, embracing diverse sources such as Greek philosopher Aristotle and Islamic and Jewish scholars. His thought exerted lasting influence on the development of Christian theology and Western philosophy. Author Anthony Kenny examines the complexities of Aquinas’s concepts of substance and accident.

The Jewish rabbi and physician Moses Maimonides, one of the greatest figures in Judaic thought, followed his contemporary Averroës in uniting Aristotelian science with religion but rejected the view that both of two conflicting systems of ideas can be true. In his Guide for the Perplexed (1190?) Maimonides attempted to provide a rational explanation of Judaic doctrine and defended religious beliefs (such as the belief in the creation of the world) that conflicted with Aristotelian science only when he was convinced that decisive evidence was lacking on either side.

The medieval theologian Saint Thomas Aquinas made a major contribution to philosophy through his interpretation of the relationship between the natural world and the divine. In this key passage from one of his most important works, Summa Theologica, he presents his views on the power - and limits - of human reason. His ideas reflect the optimism and cultural achievements of the High Middle Ages.

Abelard, Averroës, and Maimonides were each accused of blasphemy because their views conflicted with religious beliefs of the time. The 13th century, however, saw a series of philosophers who would come to be worshipped as saints. The Italian Scholastic philosopher Saint Bonaventure combined Platonic and Aristotelian principles and introduced the concept of substantial form, or nonmaterial substance, to account for the immortality of the soul. Bonaventure’s view tended toward pantheistic mysticism in making the aim of philosophy the ecstatic union with God.

This painting of the Arab philosopher Averroës appears in a series of paintings by Italian painter Andrea da Firenze in the church of Santa Maria Novella in Florence, Italy. The commentaries of Averroës on the philosophy of Aristotle had enormous influence on Christian and Jewish thinkers in Europe during the Middle Ages.

The 13th-century German Scholastic philosopher Saint Albertus Magnus was the first Christian philosopher to endorse and interpret the entire system of Aristotelian thought. He studied and admired the writings of the Muslim and Jewish Aristotelians and wrote commentaries on Aristotle in which he attempted to reconcile Aristotle’s thought with Christian teachings. He also took a great interest in the natural science of his day. The 13th-century English monk Roger Bacon, one of the first Scholastics to take an interest in experimental science, realized that a great deal remained to be learned about nature. He criticized the deductive method of his contemporaries and their reliance on past authority, and called for a new method of inquiry based on controlled observation, scientist Roger Bacon was a major advocate of experimental science during the 13th century. Bacon was condemned and imprisoned for his beliefs.

The most important medieval philosopher was Saint Thomas Aquinas, a Dominican monk who was born in Italy in 1225 and later studied under Albertus Magnus in Germany. Aquinas combined Aristotelian science and Augustinian theology into a comprehensive system of thought that later became the authoritative philosophy of the Roman Catholic Church. He wrote on every known subject in philosophy and science, and his major works, Summa Theologica and Summa Contra Gentiles, in which he presents a persuasive and systematic structure of ideas, still constitute a powerful influence on Western thought. His writings reflect the renewed interest of his time in reason, nature, and worldly happiness, together with its religious faith and concern for salvation.

During the 13th century, Saint Thomas Aquinas sought to reconcile Aristotelian philosophy with Augustinian theology. Aquinas employed both reason and faith in the study of metaphysics, moral philosophy, and religion. While Aquinas accepted the existence of God on faith, he offered five proofs of God’s existence to support such a belief.

From and through the years of 354-430, lived Saint Augustine, the greatest of the Latin Fathers and one of the most eminent Western Doctors of the Church.

Saint Augustine, born in what is now Souk-Ahras, Algeria, in ad 354, brought a systematic method of philosophy to Christian theology. Augustine taught rhetoric in the ancient cities of Carthage, Rome, and Milan before his Christian baptism in 387. His discussions of the knowledge of truth and of the existence of God drew from the Bible and from the philosophers of ancient Greece. A vigorous advocate of Roman Catholicism, Augustine developed many of his doctrines while attempting to resolve theological conflicts with Donatism and Pelagianism, two heretical Christian movements.

Augustine was born on November 13, 354, in Tagaste, Numidia (now Souk-Ahras, Algeria). His father, Patricius (died about 371), was a pagan (later converted to Christianity), but his mother, Monica, was a devout Christian who laboured untiringly for her son's conversion and who was canonized by the Roman Catholic church. Augustine was educated as a rhetorician in the former North African cities of Tagaste, Madaura, and Carthage. Between the ages of 15 and 30, he lived with a Carthaginian woman whose name is unknown; in 372 she bore him a son, whom he named Adeodatus, which is Latin for “the gift of God.”

Inspired by the philosophical treatise Hortensius, by the Roman orator and statesman Marcus Tullius Cicero, Augustine became an earnest seeker after truth. He considered becoming a Christian, but experimented with several philosophical systems before finally entering the church. For nine years, from 373 until 382, he adhered to Manichaeism, a Persian dualistic philosophy then widely current in the Western Roman Empire. With its fundamental principle of conflict between good and evil, Manichaeism at first seemed to Augustine to correspond to experience and to furnish the most plausible hypothesis upon which to construct a philosophical and ethical system. Moreover, its moral code was not very strict; Augustine later recorded in his Confessions”:Give me chastity and continence, but not just now.” Disillusioned by the impossibility of reconciling certain contradictory Manichaeist doctrines, Augustine abandoned this philosophy and turned to skepticism.

About 383 Augustine left Carthage for Rome, but a year later he went on to Milan as a teacher of rhetoric. There he came under the influence of the philosophy of Neoplatonism and met the bishop of Milan, St. Ambrose, then the most distinguished ecclesiastic in Italy. Augustine presently was attracted again to Christianity. At last one day, according to his own account, he seemed to hear a voice, like that of a child, repeating, “Take up and read.” He interpreted this as a divine exhortation to open the Scriptures and read the first passage he happened to see. Accordingly, he opened to Romans 13:13-14, where he read: “ . . . Not in revelry and drunkenness, not in debauchery and licentiousness, not in quarrelling and jealousy. But put on the Lord Jesus Christ, and make no provision for the flesh, to gratify its desires.” He immediately resolved to embrace Christianity. Along with his natural son, he was baptized by Ambrose on Easter Eve in 387. His mother, who had rejoined him in Italy, rejoiced at this answer to her prayers and hopes. She died soon afterward in Ostia.

He returned to North Africa and was ordained in 391. He became bishop of Hippo (now Annaba, Algeria) in 395, an office he held until his death. It was a period of political and theological unrest, for while the barbarians pressed in upon the empire, even sacking Rome itself in 410, schism and heresy also threatened the church. Augustine threw himself wholeheartedly into the theological battle. Besides combatting the Manichaean heresy, Augustine engaged in two great theological conflicts. One was with the Donatists, a sect that held the sacraments invalid unless administered by sinless ecclesiastics. The other conflict was with the Pelagians, followers of a contemporary British monk who denied the doctrine of original sin. In the course of this conflict, which was long and bitter, Augustine developed his doctrines of original sin and divine grace, divine sovereignty, and predestination. The Roman Catholic church has found special satisfaction in the institutional or ecclesiastical aspects of the doctrines of St. Augustine; Roman Catholic and Protestant Theology alike are largely based on their more purely theological aspects. John Calvin and Martin Luther, leaders of the Reformation, were both close students of Augustine.

Augustine's doctrine stood between the extremes of Pelagianism and Manichaeism. Against Pelagian doctrine, he held that human spiritual disobedience had resulted in a state of sin that human nature was powerless to change. In his theology, men and women are saved by the gift of divine grace; against Manichaeism he vigorously defended the place of free will in cooperation with grace. Augustine died at Hippo, August 28, 430. His feast day is August 28.

Saint Augustine, a theologian and scholar of the Roman Catholic Church, did not embrace Christianity until he was more than 30 years old, but soon after his conversion his writings became influential in a number of theological debates. Author Henry Chadwick explores several works by Augustine, including his interpretation of Genesis, the doctrine of the trinity, and his attempts to reconcile biblical views with the prevailing scientific and philosophical views of the time.

The place of prominence held by Augustine between the Fathers and Doctors of the Church is comparable to that of St. Paul among the apostles. As a writer, Augustine was prolific, persuasive, and a brilliant stylist. His best-known work is his autobiographical Confessions (circa 400), exposing his early life and conversion. In his great Christian apologia The City of God (413-26), Augustine formulated a theological philosophy of history. Ten of the 22 books of this work are devoted to polemic against pantheism. The remaining 12 books trace the origin, progress, and destiny of the church and establish it as the proper successor to paganism. In 428 Augustine wrote the Retractions, in which he registered his final verdict upon his earlier books, correcting whatever his maturer judgment held to be misleading or wrong. His other writings include the Epistles, of which 270 are in the Benedictine edition, variously dated between 386 and 429; His treatises On Free Will (388-95), On Christian Doctrine (397), On Baptism: Against the Donatists (400), On the Trinity (400-16), and On Nature and Grace (415), including Homilies upon several books of the Bible.

Saint Augustine, an influential theologian and writer in the Western Church, wrote The City of God in the 5th century. In the following excerpt from the final book, or chapter, of this work, Augustine addressed a number of theological issues, including free will and the resurrection of the faithful. He asserted that God did not deprive people of their free will even when they turned to sin because it was preferable to “bring good out of evil than to prevent the evil from coming into existence.” Augustine believed that the human body would rise after death, transformed into “the newness of the spiritual body” and in paradise these new beings would “rest and see, see and love, love and praise.”

Another, who was called Saint Thomas Aquinas, sometimes called the Angelic Doctor and the Prince of Scholastics (1225-1274), Italian philosopher and theologian, whose works have made him the most important figure in Scholastic philosophy and one of the leading Roman Catholic theologians.

During the 13th century, Saint Thomas Aquinas sought to reconcile Aristotelian philosophy with Augustinian Theology. Aquinas employed both reason and faith in the study of metaphysics, moral philosophy, and religion. While Aquinas accepted the existence of God on faith, he offered five proofs of God’s existence to support such a belief.

Aquinas was born of a noble family in Roccasecca, near Aquino, and was educated at the Benedictine monastery of Monte Cassino and at the University of Naples. He joined the Dominican order while still an undergraduate in 1243, the year of his father's death. His mother, opposed to Thomas's affiliation with a mendicant order, confined him to the family castle for more than a year in a vain attempt to make him abandon his chosen course. She released him in 1245, and Aquinas then journeyed to Paris to continue his studies. He studied under the German Scholastic philosopher Albertus Magnus, following him to Cologne in 1248. Because Aquinas was heavyset and taciturn, his fellow novices called him Dumb Ox, but Albertus Magnus is said to have predicted that “this ox will one day fill the world with his bellowing.”

Aquinas was ordained a priest about 1250, and he began to teach at the University of Paris in 1252. His first writings, primarily summaries and amplifications of his lectures, appeared two years later. His first major work was Scripta Super Libros Sententiarum (Writings on the Books of the Sentences, 1256?), Which consisted of commentaries on an influential work concerning the sacraments of the church, known as the Sententiarum Libri Quatuor (Four Books of Sentences), by the Italian theologian Peter Lombard?

In 1256 Aquinas was awarded a doctorate in theology and appointed professor of philosophy at the University of Paris. Pope Alexander IV (reigned 1254-1261) summoned him to Rome in 1259, where he acted as adviser and lecturer to the papal court. Returning to Paris in 1268, Aquinas immediately became involved in a controversy with the French philosopher Siger de Brabant and other followers of the Islamic philosopher Averroës.

The medieval theologian Saint Thomas Aquinas made a major contribution to philosophy through his interpretation of the relationship between the natural world and the divine. In this key passage from one of his most important works, Summa Theologica, he presents his views on the power - and limits - of human reason. His ideas reflect the optimism and cultural achievements of the High Middle Ages.

To understand the crucial importance of this controversy for Western thought, it is necessary to consider the context in which it occurred. Before the time of Aquinas, Western thought had been dominated by the philosophy of Saint Augustine, the Western church's great Father and Doctor of the 4th and 5th centuries, who taught that in the search for truth people must depend upon sense experience. Early in the 13th century the major works of Aristotle were made available in a Latin translation, accompanied by the commentaries of Averroës and other Islamic scholars. The vigour, clarity, and authority of Aristotle's teachings restored confidence in empirical knowledge and gave rise to a school of philosophers known as Averroists. Under the leadership of Siger de Brabant, the Averroists asserted that philosophy was independent of revelation.

Averroism threatened the integrity and supremacy of Roman Catholic doctrine and filled orthodox thinkers with alarm. To ignore Aristotle, as interpreted by the Averroists, was impossible; to condemn his teachings was ineffectual. He had to be reckoned with. Albertus Magnus and other scholars had attempted to deal with Averroism, but with little success. Aquinas succeeded brilliantly.

Reconciling the Augustinian emphasis upon the human spiritual principle with the Averroist claim of autonomy for knowledge derived from the senses, Aquinas insisted that the truths of faith and those of sense experience, as presented by Aristotle, are fully compatible and complementary. Some truths, such as that of the mystery of the incarnation, can be known only through revelation, and others, such as that of the composition of material things, only through experience; Still others, such as that of the existence of God, are known through both equally. All knowledge, Aquinas held, originates in sensation, but sense data can be made intelligible only by the action of the intellect, which elevates thought toward the apprehension of such immaterial realities as the human soul, the angels, and God. To reach understanding of the highest truths, those with which religion is concerned, the aid of revelation is needed. Aquinas's moderate realism placed the universals firmly in the mind, in opposition to extreme realism, which posited their independence of human thought. He admitted a foundation for universals in existing things, however, in opposition to nominalism and conceptualism.

Aquinas first suggested his mature position in the treatise De Unitate Intellectus Contra Averroistas (1270), which has been translated into English as The Trinity and the Unicity of the Intellect (1946). This work turned the tide against his opponents, who were condemned by the church.

Aquinas left Paris in 1272 and proceeded to Naples, where he organized a new Dominican school. In March 1274, while travailing to the Council of Lyon, to which he had been commissioned by Pope Gregory X, Aquinas fell ill. He died on March 7 at the Cistercian monastery of Fossanova.

Aquinas was canonized by Pope John XXII in 1323 and proclaimed a Doctor of the Church by Pope Pius V in 1567.

Saint Thomas Aquinas was a leading theologian and philosopher during the so-called golden age of scholasticism in the 13th century. The following passage from his Summa Theologica provides a good example of the scholastic method, which began with a question, then assembled arguments on the question that were eventually reconciled. Aquinas draws upon many authorities for his discussion, ranging from 4th-century Bc Greek philosopher Aristotle to Christian theologian Saint Augustine (ad 354-430).

More successfully than any other theologian or philosopher, Aquinas organized the knowledge of his time in the service of his faith. In his effort to reconcile faith with intellect, he created a philosophical synthesis of the works and teachings of Aristotle and other classic sages; of Augustine and other church fathers; of Averroës, Avicenna, and other Islamic scholars; of Jewish thinkers such as Maimonides and Solomon ben Yehuda ibn Gabirol; and of his predecessors in the Scholastic tradition. This synthesis he brought into line with the Bible and Roman Catholic doctrine.

Thirteenth-century Italian philosopher and theologian Saint Thomas Aquinas attempted to synthesize Christian belief with a broad range of human knowledge, embracing diverse sources such as Greek philosopher Aristotle and Islamic and Jewish scholars. His thought exerted lasting influence on the development of Christian theology and Western philosophy. Author Anthony Kenny examines the complexities of Aquinas’s concepts of substance and accident.

Aquinas's accomplishment was immense; his work marks one of the few great culminations in the history of philosophy. After Aquinas, Western philosophers could choose only between humbly following him and striking off in some altogether different direction. In the centuries immediately following his death, the dominant tendency, even among Roman Catholic thinkers, was to adopt the second alternative. Interest in Thomist philosophy began to revive, however, toward the end of the 19th century. In the encyclical Aeterni Patris (Of the Eternal Father, 1879), Pope Leo XIII recommended that St. Thomas's philosophy be made the basis of instruction in all Roman Catholic schools. Pope Pius XII, in the encyclical Humani Generis (Of the Human Race, 1950), affirmed that the Thomist philosophy is the surest guide to Roman Catholic doctrine and discouraged all departures from it. Thomism remains a leading school of contemporary thought. Among the thinkers, Roman Catholic and non-Roman Catholic alike, who have operated within the Thomist framework have been the French philosophers Jacques Maritain and Étienne Gilson.

St. Thomas was an extremely prolific author, and about 80 works are ascribed to him. The two most important are Summa Contra Gentiles (1261-1264) and Summa Theologica (1265-1273). Summa Contra Gentiles, which has been translated into English as On the Truth of the Catholic Faith (1956), is a closely reasoned treatise intended to persuade intellectual Muslims of the truth of Christianity. Summa Theologica, which has been republished frequently in Latin and vernacular editions under its Latin title, was written in three parts (on God, on the moral life, and on Christ) and was intended to set forth Christian doctrine for beginners. The last part remained unfinished at his death.

At this point a Scholasticism, began as the philosophic and theological movement that attempted to use natural human reason, in particular, the philosophy and science of Aristotle, to understand the supernatural content of Christian revelation. It was dominant in the medieval Christian schools and universities of Europe from about the middle of the 11th century to about the middle of the 15th century. The ultimate ideal of the movement was to integrate of an ordered system both the natural wisdom of Greece and Rome and the religious wisdom of Christianity. The term Scholasticism is also used in a wider sense to signify the spirit and methods characteristic of this period of thought or any similar spirit and attitude toward learning found in other periods of history. The term Scholastic, which originally designated the heads of the medieval monastic or cathedral schools from which the universities developed, finally came to be applied to anyone teaching philosophy or theology in such schools or universities.

Saint Thomas Aquinas was a leading theologian and philosopher during the so-called golden age of scholasticism in the 13th century. The following passage from his Summa Theologica provides a good example of the scholastic method, which began with a question, then assembled arguments on the question that were eventually reconciled. Aquinas draws upon many authorities for his discussion, ranging from 4th-century Bc Greek philosopher Aristotle to Christian theologian Saint Augustine (ad 354-430).

Scholastic thinkers held a wide variety of doctrines in both philosophy and theology. What gives unity to the whole Scholastic movement are the common aims, attitudes, and methods generally accepted by all its members? The chief concern of the Scholastics was not to discover new facts but to integrate the knowledge already acquired separately by Greek reasoning and Christian revelation. This concern is one of the most characteristic differences between Scholasticism and modern thought since the Renaissance.

The basic aim of the Scholastics determined certain common attitudes, the most important of which was their conviction of the fundamental harmony between reason and revelation. The Scholastics maintained that because the same God was the source of both types of knowledge and truth was one of his chief attributes, he could not contradict himself in these two ways of speaking. Any apparent opposition between revelation and reason could be traced either to an incorrect use of reason or to an inaccurate interpretation of the words of revelation. Because the Scholastics believed that revelation was the direct teaching of God, it possessed for them a higher degree of truth and certitude than did natural reason. In apparent conflicts between religious faith and philosophic reasoning, faith was thus always the supreme arbiter; the theologian's decision overruled that of the philosopher. After the early 13th century, Scholastic thought emphasized more the independence of philosophy within its own domain. Nonetheless, throughout the Scholastic period, philosophy was called the servant of theology, not only because the truth of philosophy was subordinated to that of theology, but also because the theologian used philosophy to understand and explain revelation.

This attitude of Scholasticism stands in sharp contrast to the so-called double-truth theory of the Spanish-Arab philosopher and physician Averroës. His theory assumed that truth was accessible to both philosophy and Islamic theology but that only philosophy could attain it perfectly. The so-called truths of theology served, hence, as imperfect imaginative expressions for the common people of the authentic truth accessibly only to philosophy. Averroës maintained that philosophic truth could even contradict, at least verbally, the teachings of Islamic theology.

As a result of their belief in the harmony between faith and reason, the Scholastics attempted to determine the precise scope and competence of each of these faculties. Many early Scholastics, such as the Italian ecclesiastic and philosopher St. Anselm, did not clearly distinguish the two and were overconfident that reason could prove certain doctrines of revelation. Later, at the height of the mature period of Scholasticism, the Italian theologian and philosopher St. Thomas Aquinas worked out a balance between reason and revelation. Scholastics after Aquinas, however, beginning with the Scottish theologian and philosopher John Duns Scotus, restricted more and more the domain of truths capable of being proved by reason and insisted that many doctrines previously thought to have been proved by philosophy had to be accepted on the basis of faith alone. One reason for this restriction was that Scholastics applied the requirements for scientific demonstration, as first specified in Aristotle's Organon, much more rigorously than previous philosophers had done. These requirements were so strict that Aristotle himself was rarely able to apply them fully beyond the realm of mathematics. It was this trend that led finally to the loss of confidence in natural human reason and philosophy that is characteristic of the early Renaissance and of the first Protestant religious reformers, such as Martin Luther.

Another common attitude among Scholastics was their great respect for the so-called authorities in both philosophy and theology. These authorities were the great philosophers of Greece and Rome and the early Fathers of the Church. The medieval Scholastics educated themselves to think and write only by intensive study of these ancient authors, whose culture and learning had been so much richer than their own. After they had reached their full maturity of thought and had begun to create original works of philosophy, they continued the practice of quoting authorities to lend weight to their own opinions, even though the latter were reached, in many cases, quite independently. Later critics concluded from this practice that the Scholastics were mere compilers or repeaters of their authorities. As a matter of fact, the mature Scholastics, including Aquinas and Duns Scotus, were extremely flexible and independent in their use of the texts of the ancients; frequently, in order to bring the texts into harmony with their own positions, they gave interpretations that were difficult to reconcile with the ancients' intentions. The appeal to authority was often little more than a stylistic ornament for beginning or ending the exposition of the commentator's own opinions and was intended to show that the commentator's views were in continuity with the past and not mere novelties. Novelty and originality of thought were not sought deliberately by any of the Scholastics but were rather underplayed as much as possible.

The Scholastics considered Aristotle the chief authority in philosophy, calling him simply the Philosopher. The early Christian prelate and theologian St. Augustine was their principal authority in theology, subordinate only to the Bible and the official councils of the church. The Scholastics adhered most closely and uncritically to authority in accepting Aristotle's opinions in the empirical sciences, such as physics, astronomy, and biology. Their uncritical acceptance of Aristotle's scientific views produced a serious weakness in Scholasticism and was one of the principal reasons for its scornful rejection by scientists during the Renaissance and later.

One of the principal methods of Scholasticism was the use of the logic and philosophic vocabulary of Aristotle in teaching, demonstration, and discussion. Another important method was the practice of teaching a text by means of a commentary by some accepted authority. In philosophy, this authority was usually Aristotle. In theology, the principal texts were the Bible and the Sententiarum Libri Quatuor (Four Books of Sentences) by the 12th-century Italian theologian and prelate Peter Lombard, a collection of the opinions of the early Fathers of the Church on problems of theology. The early Scholastics began by adhering closely to the text on which they were commenting. Gradually, as the practice of critical reading developed their own powers of thinking, they began to introduce many supplementary commentaries on points, known as disputed questions, which either were not covered or were not adequately solved by the text itself. Beginning in the 13th century these supplementary commentaries, embodying the personal thought of the teachers, became the largest and most important part of the commentaries, with the result that literal explanation of the text was reduced to a mere fraction of each commentary.

Closely allied with the commentaries on disputed questions was the technique of discussion by means of public disputation. Every professor in a medieval university was required to appear several times a year before the assembled faculty and students in a disputation, defending crucial points of his own teaching against all persons who challenged them. The forms of Aristotelian logic were employed in both defence and attack. In the 13th century the public disputation became a flexible educational tool for stimulating, testing, and communicating the progress of thought in philosophy and theology. After the middle of the 14th century, however, the vitality of public disputation declined, and it became a rigid formalism. Disputants became concerned less with real content and more with fine points of logic and minute subtleties of thought. This degraded form of disputation did much to give Scholasticism a bad reputation during the Renaissance and later; consequently, many modern thinkers have considered it mere pedantic logical formalism.

During the 13th century, Saint Thomas Aquinas sought to reconcile Aristotelian philosophy with Augustinian theology. Aquinas employed both reason and faith in the study of metaphysics, moral philosophy, and religion. While Aquinas accepted the existence of God on faith, he offered five proofs of God’s existence to support such a belief.

The outstanding Scholastics of the 11th and 12th centuries included Anselm, the French philosopher, theologian, and teacher of logic Peter Abelard, and the philosopher and clergyman Roscelin, who founded the school of philosophy known as nominalism. Among Jewish thinkers of the same period, the rabbi, philosopher, and physician Maimonides attempted to reconcile Aristotelian philosophy with divine revelation, as understood in Judaism, in a spirit similar to that of the Christian Scholastics. The Scholastics of the so-called golden age of the 13th century included Aquinas and the German philosopher St. Albertus Magnus, both of the Dominican order; the English monk and philosopher Roger Bacon, the Italian prelate and theologian St. Bonaventure, and Duns Scotus, all of the Franciscan order; and the Belgian secular priest Henry of Ghent (1217? -1293). Nominalism became the dominant school of philosophy in the 14th century, when Scholasticism began to decline. The most important nominalist was the English philosopher William of Ockham, a great logician who attacked all the philosophic systems of the preceding Scholastics and maintained that natural reason and philosophy had a much more restricted field of operation than his predecessors had held to be the case.

Thirteenth-century Italian philosopher and theologian Saint Thomas Aquinas attempted to synthesize Christian belief with a broad range of human knowledge, embracing diverse sources such as Greek philosopher Aristotle and Islamic and Jewish scholars. His thought exerted lasting influence on the development of Christian theology and Western philosophy. Author Anthony Kenny examines the complexities of Aquinas’s concepts of substance and accident.

A brilliant but brief revival of Scholasticism, especially in the field of theology, took place in Spain in the 16th century, chiefly among the Dominicans, as exemplified by the Spanish theologian Francisco de Vitoria, and the Jesuits, as exemplified by the Spanish theologian and philosopher Francisco Suárez. A more widespread revival was launched by Pope Leo XIII in 1879 with the purpose of reconsidering, in the light of modern needs, the great Scholastic systems of the 13th century, especially that of Aquinas, and of incorporating in a modern reformulation of those systems all the genuine contributions of modern thought. This revival, which has often been called neo-Scholasticism, is one of the established currents of contemporary thought. The principal exponents of neo-Scholasticism include the French philosopher and diplomat Jacques Maritain and the French philosopher and historian of philosophy Étienne Henri Gilson.

Even, Aristotle's works were lost in the West after the decline of Rome. During the 9th century ad, Arab scholars introduced Aristotle, in Arabic translation, to the Islamic world (see Islam). The 12th-century Spanish-Arab philosopher Averroës is the best known of the Arabic scholars who studied and commented on Aristotle. In the 13th century, the Latin West renewed its interest in Aristotle's work, and Saint Thomas Aquinas found in it a philosophical foundation for Christian thought. Church officials at first questioned Aquinas's use of Aristotle; in the early stages of its rediscovery, Aristotle's philosophy was regarded with some suspicion, largely because his teachings were thought to lead to a materialistic view of the world. Nevertheless, the work of Aquinas was accepted, and the later philosophy of scholasticism continued the philosophical tradition based on Aquinas's adaptation of Aristotelian thought.

Aquinas made many important investigations into the philosophy of religion, including an extremely influential study of the attributes of God, such as omnipotence, omniscience, eternity, and benevolence. He also provided a new account of the relationship between faith and reason, arguing against the Averroists that the truths of faith and the truths of reason cannot conflict but rather apply to different realms. The truths of natural science and philosophy are discovered by reasoning from facts of experience, whereas the tenets of revealed religion, the doctrine of the Trinity, the creation of the world, and other articles of Christian dogma are beyond rational comprehension, although not inconsistent with reason, and must be accepted on faith. The metaphysics, theory of knowledge, ethics, and politics of Aquinas were derived mainly from Aristotle, but he added the Augustinian virtues of faith, hope, and charity and the goal of eternal salvation through grace to Aristotle’s naturalistic ethics with its goal of worldly happiness.

The most important critics of Thomistic philosophy (adherence to the theories of Aquinas) were the 13th-century Scottish theologian John Duns Scotus and 14th-century English Scholastic William of Ockham. Duns Scotus developed a subtle and highly technical system of logic and metaphysics, but because of the fanaticism of his followers the name Duns later ironically became a symbol of stupidity in the English word dunce. Scotus rejected the attempt of Aquinas to reconcile rational philosophy with revealed religion. He maintained, in a modified version of the double-truth doctrine of Averroës, that all religious beliefs are matters of faith, except for the belief in the existence of God, which he regarded as logically provable. Against the view of Aquinas that God acts in accordance with his rational nature, Scotus argued that the divine will is prior to the divine intellect and creates, rather than follows, the laws of nature and morality, thus implying a stronger notion of free will than that of Aquinas. On the issue of universals, Scotus developed a new compromise between realism and nominalism, accounting for the difference between individual objects and the forms that these objects exemplify as a logical rather than a real distinction.

William of Ockham formulated the most radically nominalistic criticism of the Scholastic belief in intangible, invisible things such as forms, essences, and universals. He maintained that such abstract entities are merely references of words to other words rather than to actual things. His famous rule, known as Ockham’s razor—which said that one should not assume the existence of more things than are logically necessary—became a fundamental principle of modern science and philosophy.

In the 15th and 16th centuries a revival of scientific interest in nature was accompanied by a tendency toward pantheistic mysticism - that is, finding God in all things. The Roman Catholic prelate Nicholas of Cusa anticipated the work of the Polish astronomer Nicolaus Copernicus in his suggestion that the Earth moved around the Sun, thus displacing humanity from the centre of the universe; he also conceived of the universe as infinite and identical with God. The Italian philosopher Giordano Bruno, who similarly identified the universe with God, developed the philosophical implications of the Copernican theory. Bruno’s philosophy influenced subsequent intellectual forces that led to the rise of modern science and to the Reformation.

The word modern in philosophy originally meant “new,” distinguishing a new historic era both from antiquity and from the intervening Middle Ages. Many things had occurred in the intellectual, religious, political, and social life of Europe to justify the belief of 16th-and-17th-century thinkers in the genuinely new character of their times. The explorations of the world; the Protestant Reformation, with its emphasis on individual faith; the rise of commercial urban society; and the dramatic appearance during the Renaissance of new ideas in all areas of culture stimulated the development of a new philosophical world-view.

The medieval view of the world as a hierarchical order of beings created and governed by God was supplanted by the mechanistic picture of the world as a vast machine, the parts of which move in accordance with strict physical laws, without purpose or will. In this view of the universe, known as Mechanism, science took precedence over spirituality, and the surrounding physical world that we experience and observe received as much, if not more, attention than the world to come. The aim of human life was no longer conceived as preparation for salvation in the next world, but rather as the satisfaction of people’s natural desires. Political institutions and ethical principles ceased to be regarded as reflections of divine command and came to be seen as practical devices created by humans.

The human mind itself seemed an inexhaustible reality, on a par with the physical reality of matter. Modern philosophers had the task of defining more clearly the essence of mind and of matter, and of reasoning about the relation between the two. Individuals ought to see for themselves, they believed, and study the “book of Nature,” and in every case search for the truth with their own reason.

Since the 15th century modern philosophy has been marked by a continuing interaction between systems of thought based on a mechanistic, materialistic interpretation of the universe and those founded on a belief in human thought as the only ultimate reality. This interaction has reflected the increasing effect of scientific discovery and political change on philosophical speculation.

This painting from the 19th century depicts Italian scientist Galileo at the Vatican in Rome in the 17th century. Galileo was forced to stand trial for his belief in Copernicanism, or the idea that Earth moves around the Sun. The Roman Catholic Church forced Galileo to publicly denounce Copernicanism and spend the rest of his life under house arrest.

In the new philosophical climate, experience and reason became the sole standards of truth. The first great spokesperson for the new philosophy was the English philosopher and statesman Francis Bacon, who denounced reliance on authority and verbal argument and criticized Aristotelian logic as useless for the discovery of new laws. Bacon called for a new scientific method based on reasoned generalization from careful observation and experiment. He was the first to formulate rules for this new method of drawing conclusions, now known as inductive inference (see Induction).

English philosopher and statesman Sir Francis Bacon’s philosophical treatise, Novum Organum (1620), is regarded as an important contribution to scientific methodology. In this work Bacon advanced the necessity of experimentation and accurate observation. Writing in aphorisms (concise statements of principle), Bacon outlined four types of false notions or methods that impede the ability to study nature impartially. He labelled these notions the Idols of the Tribe, the Idols of the Cave, the Idols of the Market-place, and the Idols of the Theatre. Novum Organum greatly influenced the later empiricists, including English philosopher John Locke.

The work of Italian physicist and astronomer Galileo was of even greater importance in the development of a new world-view. Galileo brought attention to the importance of applying mathematics to the formulation of scientific laws. This he accomplished by creating the science of mechanics, which applied the principles of geometry to the motions of bodies. The success of mechanics in discovering reliable and useful laws of nature suggested to Galileo and to later scientists that all nature is designed in accordance with mechanical laws.

The struggle between the Roman Catholic Church and 17th-century Italian physicist and astronomer Galileo has become symbolic of the clash between authority and intellectual freedom, but Galileo himself did not foresee any conflict. Using one of the first telescopes, Galileo found evidence to support the Copernican theory that the Earth and the other planets revolved around the Sun. Galileo believed that his scientific findings fell far outside the theological realm. Author Stillman Drake explores Galileo’s shock and disbelief as his disagreement with the church escalated.

These great changes of the 15th and 16th centuries brought about two intellectual crises that profoundly affected Western civilization. First, the decline of Aristotelian science called into question the methods and foundations of the sciences. This decline came about for a number of reasons including the inability of Aristotelian principles to explain new observations in astronomy. Second, new attitudes toward religion undermined religious authority and gave agnostic and atheistic ideas a chance to be heard.

French philosopher and mathematician René Descartes (1596-1650) is sometimes called the father of modern philosophy. In 1649 Descartes was invited by Queen Christina of Sweden to Stockholm to instruct the queen in philosophy. Although treated well by the queen, he was unaccustomed to the cold of Swedish winters and died of pneumonia the following year.

During the 17th century French mathematician, physicist, and philosopher René Descartes attempted to resolve both crises. He followed Bacon and Galileo in criticizing existing methods and beliefs, but whereas Bacon had argued for an inductive method based on observed facts, Descartes made mathematics the model for all science. Descartes championed the truth contained in the “clear and distinct ideas” of reason itself. The advance toward knowledge was from one such truth to another, as in mathematical reasoning. Descartes believed that by following his rationalist method, one could establish first principles (fundamental underlying truths) for all knowledge — about man, the world, and even God.

The 17th century French scientist and mathematician René Descartes was also one of the most influential thinkers in Western philosophy. Descartes stressed the importance of skepticism in thought and proposed the idea that existence had a dual nature: one physical, the other mental. The latter concept, known as Cartesian dualism, continues to engage philosophers today. This passage from Discourse on Method (first published in his Philosophical Essays in 1637) contains a summary of his thesis, which includes the celebrated phrase “I think: Therefore? I am.”

Descartes resolved to reconstruct all human knowledge on an absolutely certain foundation by refusing to accept any belief, even the belief in his own existence, until he could prove it to be necessarily true. In his so-called dream argument, he argued that our inability to prove with certainty when we are awake and when we are dreaming makes most of our knowledge uncertain. Ultimately he concluded that the first thing of whose existence one can be certain is oneself as a thinking being. This conclusion forms the basis of his well-known argument, “Cogito, ergo sum” (“I think: Therefore? I am”). He also argued that, in pure thought, one has a clear conception of God and can demonstrate that God exists. Descartes argued that secure knowledge of the reality of God allowed him to have his earlier doubts about knowledge and science.

French thinker René Descartes applied rigorous scientific methods of deduction to his exploration of philosophical questions. Descartes is probably best known for his pioneering work in philosophical skepticism. Author Tom Sorell examines the concepts behind Descartes’s work Meditationes de Prima Philosophia (1641; Meditations on First Philosophy), focussing on its unconventional use of logic and the reactions it aroused.

Despite his mechanistic outlook, Descartes accepted the traditional religious doctrine of the immortality of the soul and maintained that mind and body are two distinct substances, thus exempting mind from the mechanistic laws of nature and providing for freedom of the will. His fundamental separation of mind and body, known as dualism, raised the problem of explaining how two such different substances as mind and body can affect each other, a problem he was unable to solve since which has remained a concern of philosophy ever. Descartes’s thought launched an era of speculation in metaphysics as philosophers made a determined effort to overcome dualism -the belief in the irreconcilable difference between mind and matter - and obtain unity. The separation of mind and matter is also known as Cartesian dualism after Descartes.

The 17th–century English philosopher Thomas Hobbes, in his effort to attain unity, asserted that matter is the only real substance. He constructed a comprehensive system of metaphysics that provided a solution to the mind-body problem by reducing mind to the internal motions of the body. He also argued that there is no contradiction between human freedom and causal determinism — the view that every act is determined by a prior cause. Both, according to Hobbes, work in accordance with the mechanical laws that govern the universe.

Seventeenth-century English philosopher Thomas Hobbes’s view of human nature is often characterized as deeply pessimistic. In the famous phrase from Leviathan (1651), Hobbes’s best–known work, “the life of man is nasty, brutish, and short.” This excerpt from a study of Hobbes’s work by author Richard Tuck makes it clear, however, that Hobbes developed his theory of human morality and social relations from the humanist tradition prevalent among intellectuals of his time.

In his ethical theory Hobbes derived the rules of human behaviour from the law of self-preservation and justified egoistic action as the natural human tendency. In his political theory he maintained that government and social justice are artificial creations based on social contract (voluntary agreement between people and their government) and maintained by force. In his most famous work, Leviathan (1651), Hobbes justified political authority on the basis that self-interested people who existed in a terrifying “state of nature” - that is, without a ruler - would seek to protect themselves by forming a political commonwealth that had rules and regulations. He concluded that absolute monarchy is the most effective means of preserving peace.

A member of the rationalist school of philosophy, Baruch Spinoza pursued knowledge through deductive reasoning rather than induction from sensory experience. Spinoza applied the theoretical method of mathematics to other realms of inquiry. Following the format of Euclid’s Elements, Spinoza’s Ethics organized morality and religion into definitions, axioms, and postulates.

Whereas Hobbes tried to oppose Cartesian dualism by reducing mind to matter, the 17th-century Dutch philosopher Baruch Spinoza attempted to reduce matter to divine spiritual substance. He constructed a remarkably precise and rigorous system of philosophy that offered new solutions to the mind-body problem and to the conflict between religion and science. Like Descartes, Spinoza maintained that the entire structure of nature can be deduced from a few basic definitions and axioms, on the model of Euclidean geometry. However, Spinoza believed that Descartes’s theory of two substances created an insoluble problem of the way in which mind and bodies interact. He concluded that the ultimate substance is God and that God, substance, and nature are identical. Thus he supported the pantheistic view that all things are aspects or modes of God (see Pantheism).

Dutch philosopher Baruch Spinoza is regarded as the foremost Western proponent of pantheism, the belief that God and nature are one and the same. This idea is the central thesis of Spinoza’s most famous and influential work, the 1674 Ethica Ordine Geometrico Demonstrata (Ethics Demonstrated with Geometrical Order). Author Roger Scruton examines Spinoza’s assertion that God is the “substance” of everything.

Spinoza’s solution to the mind-body problem explained the apparent interaction of mind and body by regarding them as two forms of the same substance, which exactly parallel each other, thus seeming to affect each other but not really doing so. Spinoza’s ethics, like the ethics of Hobbes, was based on materialistic psychology according to which individuals are motivated only by self-interest. But in contrast to Hobbes, Spinoza concluded that rational self-interest coincides with the interest of others.

English philosopher John Locke explained his theory of empiricism, a philosophical doctrine holding that all knowledge is based on experience, in An Essay Concerning Human Understanding (1690). Locke believed the human mind to be a blank slate at birth that gathered all its information from its surroundings - starting with simple ideas and combining these simple ideas into more complex ones. His theory greatly influenced education in Great Britain and the United States. Locke believed that education should begin in early childhood and should proceed gradually as the child learns increasingly complex ideas.

English philosopher John Locke responded to the challenge of Cartesian dualism by supporting a commonsense view that the corporeal (bodily or material) and the spiritual are simply two parts of nature that remain always present in human experience. He made no attempt rigorously to define these parts of nature or to construct a detailed system of metaphysics that attempted to explain them; Locke believed that such philosophical aims were impossible to carry out and thus pointless. Against the rationalism of Descartes and Spinoza, who believed in the ability to achieve knowledge through reasoning and logical deduction, Locke continued the empiricist tradition begun by Bacon and embraced by Hobbes. The empiricists believed that knowledge came from observation and sense perceptions rather than from reason alone.

In 1690 Locke gave empiricism a systematic framework with the publication of his Essay Concerning Human Understanding. Of particular importance was Locke’s redirection of philosophy away from the study of the physical world and toward the study of the human mind. In so doing he made epistemology, the study of the nature of knowledge, the principal concern of philosophy in the 17th and 18th century. In his own theory of the mind Locke attempted to reduce all ideas to simple elements of experience, but he distinguished sensation and reflection as sources of experience, sensation providing the material for knowledge of the external world, and reflection the material for knowledge of the mind.

Locke greatly influenced the skepticism of later British thinkers, such as George Berkeley and David Hume, by recognizing the vagueness of the concepts of metaphysics and by pointing out that inferences about the world outside the mind cannot be proved with certainty. His ethical and political writings had an equally great influence on subsequent thought. During the late 18th century the founders of the modern school of utilitarianism, which makes happiness for the largest possible number of people the standard of right and wrong, drew heavily on the writings of Locke. His defence of constitutional government, religious tolerance, and natural human rights influenced the development of liberal thought during the late 18th century in France and the United States as well as in Great Britain.

Efforts to resolve the dualism of mind and matter, a problem first raised by Descartes, continued to engage philosophers during the 17th and 18th centuries. The division between science and religious belief also occupied them. There, the aim was to preserve the essentials of faith in God while at the same time defending the right to think freely. One view called Deism saw God as the cause of the great mechanism of the world, a view more in harmony with science than with traditional religion. Natural science at this time was striding ahead, relying on sense perception as well as reason, and thereby discovering the universal laws of nature and physics. Such empirical (observation-based) knowledge appeared to be more certain and valuable than philosophical knowledge based upon reason alone.

After Locke philosophers became more sceptical about achieving knowledge that they could be certain was true. Some thinkers who despaired of finding a resolution to dualism embraced skepticism, the doctrine that true knowledge, other than what we experience through the senses, is impossible. Others turned to increasingly radical theories of being and knowledge. Among them was German philosopher Immanuel Kant, probably the most influential of all because he set Western philosophy on a new path that it still follows today. Kant’s view that knowledge of the world is dependent upon certain innate categories or ideas in the human mind is known as idealism.

Nevertheless, finding to a theory that magnifies the role of decisions, or free selection from among equally possible alternatives, in order to show that what appears to be objective or fixed by nature is in fact an artefact of human convention, similar to conventions of etiquette, or grammar, or law. Thus one might suppose that moral rules owe more to social convention than to anything imposed from outside, or that supposedly inexorable necessities are in fact the shadow of our linguistic conventions. The disadvantage of conventionalism is that it must show that alternative, equally workable conventions could have been adopted, and it is often easy to believe that, for example, if we hold that some ethical norm such as respect for promises or property is conventional, we ought to be able to show that human needs would have been equally well satisfied by a system involving a different norm, and this may be hard to establish.

A convention also suggested by Paul Grice (1913-88) directing participants in conversation to pay heed to an accepted purpose or direction of the exchange. Contributions made without paying this attention are liable to be rejected for other reasons than straightforward falsity: Something rue but unhelpful or inappropriate may meet with puzzlement or rejection. We can thus never infer fro the fact that it would be inappropriate to say something in some circumstance that what would be aid, were we to say it, would be false. This inference was frequently and in ordinary language philosophy, it being argued, for example, that since we do not normally say ‘there sees to be a barn there’ when there is unmistakably a barn there, it is false that on such occasions there seems to be a barn there.

There are two main views on the nature of theories. According to the ‘received view’ theories are partially interpreted axiomatic systems, according to the semantic view, a theory is a collection of models (Suppe, 1974). However, a natural language comes ready interpreted, and the semantic problem is no that of the specification but of understanding the relationship between terms of various categories (names, descriptions, predicates, adverbs . . .) and their meanings. An influential proposal is that this relationship is best understood by attempting to provide a ‘truth definition’ for the language, which will involve giving terms and structure of different kinds have on the truth-condition of sentences containing them.

The axiomatic method . . . as, . . . a proposition lid down as one from which we may begin, an assertion that we have taken as fundamental, at least for the branch of enquiry in hand. The axiomatic method is that of defining as a set of such propositions, and the ‘proof procedures’ or finding of how a proof ever gets started. Suppose I have as premises (1) p and (2) p ➞ q. Can I infer q? Only, it seems, if I am sure of, (3) (p & p ➞q) ➞q. Can I then infer q? Only, it seems, if I am sure that (4) (p & p ➞ q) ➞ q) ➞ q. For each new axiom (N) I need a further axiom (N + 1) telling me that the set so far implies q, and the regress never stops. The usual solution is to treat a system as containing not only axioms, but also rules of reference, allowing movement fro the axiom. The rule ‘modus ponens’ allow us to pass from the first two premises to q. Charles Dodgson Lutwidge (1832-98) better known as Lewis Carroll’s puzzle shows that it is essential to distinguish two theoretical categories, although there may be choice about which to put in which category.

This type of theory (axiomatic) usually emerges as a body of (supposes) truths that are not nearly organized, making the theory difficult to survey or study a whole. The axiomatic method is an idea for organizing a theory (Hilbert 1970): one tries to select from among the supposed truths a small number from which all others can be seen to be deductively indexable. This makes the theory rather more tractable since, in a sense, all the truths are contained in those few. In a theory so organized, the few truths from which all others are deductively inferred are called axioms. In that, just as algebraic and differential equations, which were used to study mathematical and physical processes, could they be made mathematical objects, so axiomatic theories, like algebraic and differential equations, which are means of representing physical processes and mathematical structures, could be made objects of mathematical investigation.

In the traditional (as in Leibniz, 1704), many philosophers had the conviction that all truths, or all truths about a particular domain, followed from a few principles. These principles were taken to be either metaphysically prior or epistemologically prior or in the fist sense, they were taken to be entities of such a nature that what exists is ‘caused’ by them. When the principles were taken as epistemologically prior, that is, as axioms, they were taken to be epistemologically privileged either, e.g., self-evident, not needing to be demonstrated or (again, inclusive ‘or’) to be such that all truths do follow from them (by deductive inferences). Gödel (1984) showed that treating axiomatic theories as themselves mathematical objects, that mathematics, and even a small part of mathematics, elementary number theory, could not be axiomatized, that, more precisely, any class of axioms that in such that we could effectively decide, of any proposition, whether or not it was in the class, would be too small to capture all of the truths.

The use of a model to test for the consistency of an axiomatized system is older than modern logic. Descartes’s algebraic interpretation of Euclidean geometry provides a way of showing that if the theory of real numbers is consistent, so is the geometry. Similar mapping had been

used by mathematicians in the 19th century for example to show that if Euclidean geometry is consistent, so are various non-Euclidean geometries. Model theory is the general study of this kind of procedure: The study of interpretations of formal system. Proof theory studies relations of deductibility as defined purely syntactically, that is, without reference to the intended interpretation of the calculus. More formally, a deductively valid argument starting from true premises, that yields the conclusion between formulae of a system. But once the notion of an interpretation is in place we can ask whether a formal system meets certain conditions. In particular, can it lead us from sentences that are true under some interpretation to ones that are false under the same interpretation? And if a sentence is true under all interpretations, is it also a theorem of the system? We can define a notion of validity (a formula is valid if it is true in all interpretations) and semantic consequence (a formula, written {A1 . . . An} ⊨ B, if it is true in all interpretations in which they are true) The central questions for a calculus will be whether all and only its theorems are valid, and whether {A1 . . . An} ⊨ B, if and only if {A1. . . . An} ⊢ B. These are the questions of the soundness and completeness of a formal system. For the propositional calculus this turns into the question of whether the proof theory delivers as theorems all and only tautologies. There are many axiomatizations of the propositional calculus that are consistent an complete. Gödel proved in 1929 that first-order predicate calculus is complete: any formula that is true under every interpretation is a theorem of the calculus.

The propositional calculus or logical calculus whose expressions are character representation sentences or propositions, and constants representing operations on those propositions to produce others of higher complexity. The operations include conjunction, disjunction, material implication and negation (although these need not be primitive). Propositional logic was partially anticipated by the Stoics but researched maturity only with the work of Frége, Russell, and Wittgenstein.

The concept introduced by Frége of a function taking a number of names as arguments, and delivering one proposition as the value. The idea is that ‘χ loves y’ is a propositional function, which yields the proposition ‘John loves Mary’ from those two arguments (in that order). A propositional function is therefore roughly equivalent to a property or relation. In Principia Mathematica, Russell and Whitehead take propositional functions to be the fundamental function, since the theory of descriptions could be taken as showing that other expressions denoting functions are incomplete symbols.

Keeping in mind, the two classical truth-values that a statement, proposition, or sentence can take. It is supposed in classical (two-valued) logic, that each statement has one of these values, and none has both. A statement is then false if and only if it is not true. The basis of this scheme is that to each statement there corresponds a determinate truth condition, or way the world must be for it to be true, and otherwise false. Statements may be felicitous or infelicitous in other dimensions (polite, misleading, apposite, witty, etc.) but truth is the central normative governing assertion. Considerations of vagueness may introduce greys into a black-and-white scheme. For the issue of whether falsity is the only way of failing to be true.

Formally, it is nonetheless, that any suppressed premise or background framework of thought necessary to make an argument valid, or a position tenable. More formally, a presupposition has been defined as a proposition whose truth is necessary for either the truth or the falsity of another statement. Thus, if ‘p’ presupposes ‘q’, ‘q’ must be true for p to be either true or false. In the theory of knowledge of Robin George Collingwood (1889-1943), any propositions capable of truth or falsity stand on a bed of ‘absolute presuppositions’ which are not properly capable of truth or falsity, since a system of thought will contain no way of approaching such a question. It was suggested by Peter Strawson (1919-), in opposition to Russell’s theory of ‘definite’ descriptions, that ‘there exists a King of France’ is a presupposition of ‘the King of France is bald’, the latter being neither true, nor false, if there is no King of France. It is, however, a little unclear whether the idea is that no statement at all is made in such a case, or whether a statement I can made, but fails of being one a true and oppose of either true ids false. The former option preserves classical logic, since we can still say that every statement is either true or false, but the latter does not, since in classical logic the law of ‘bivalence’ holds, and ensures that nothing at all is presupposed for any proposition to be true or false. The introduction of presupposition therefore means that either a third truth-value is found, ‘intermediate’ between truth and falsity, or classical logic is preserved, but it is impossible to tell whether a particular sentence expresses a proposition that is a candidate for truth ad falsity, without knowing more than the formation rules of the language. Each suggestion carries costs, and there is some consensus that at least where definite descriptions are involved, examples like the one given are equally well handed by regarding the overall sentence false when the existence claim fails.

A proposition may be true or false it is said to take the truth-value true, and if the latter the truth-value false. The idea behind the term is the analogy between assigning a propositional variable one or other of these values, as a formula of the propositional calculus, and assigning an object as the value of many other variable. Logics with intermediate values are called many-valued logics. Then, a truth-function of a number of propositions or sentences is a function of them that has a definite truth-value, depends only on the truth-values of the constituents. Thus (p & q) is a combination whose truth-value is true when ‘p’ is true and ‘q’ is true, and false otherwise, ¬ p is a truth-function of ‘p’, false when ‘p’ is true and true when ‘p’ is false. The way in which the value of the whole is determined by the combinations of values of constituents is presented in a truth table.

In whatever manner, truths of fact cannot be reduced to any identity and our only way of knowing them is a posteriori, by reference to the facts of the empirical world.

A proposition is knowable a priori if it can be known without experience of the specific course of events in the actual world. It may, however, be allowed that some experience is required to acquire the concepts involved in an a priori proposition. Some thing is knowable only a posteriori if it can be known a priori. The distinction given one of the fundamental problem areas of epistemology. The category of a priori propositions is highly controversial, since it is not clear how pure thought, unaided by experience, can give rise to any knowledge at all, and it has always been a concern of empiricism to deny that it can. The two great areas in which it seems to be so are logic and mathematics, so empiricists have commonly tried to show either that these are not areas of real, substantive knowledge, or that in spite of appearances their knowledge that we have in these areas is actually dependent on experience. The former line tries to show sense trivial or analytic, or matters of notation conventions of language. The latter approach is particularly associated with Quine, who denies any significant slit between propositions traditionally thought of as a priori, and other deeply entrenched beliefs that occur in our overall view of the world.

Another contested category is that of a priori concepts, supposed to be concepts that cannot be ‘derived’ from experience, but which are presupposed in any mode of thought about the world, time, substance, causation, number, and self are candidates. The need for such concept s, and the nature of the substantive a prior knowledge to which they give rise, is the central concern of Kant ‘s Critique of Pure Reason.

Likewise, since their denial does not involve a contradiction, there is merely contingent: Their could have been in other ways a hold of the actual world, but not every possible one. Some examples are ‘Caesar crossed the Rubicon’ and ‘Leibniz was born in Leipzig’, as well as propositions expressing correct scientific generalizations. In Leibniz’s view truths of fact rest on the principle of sufficient reason, which is a reason why it is so. This reason is that the actual world (by which he means the total collection of things past, present and future) is better than any other possible world and therefore created by God. The foundation of his thought is the conviction that to each individual there corresponds a complete notion, knowable only to God, from which is deducible all the properties possessed by the individual at each moment in its history. It is contingent that God actualizes te individual that meets such a concept, but his doing so is explicable by the principle of ‘sufficient reason’, whereby God had to actualize just that possibility in order for this to be the best of all possible worlds. This thesis is subsequently lampooned by Voltaire (1694-1778), in whom of which was prepared to take refuge in ignorance, as the nature of the soul, or the way to reconcile evil with divine providence.

In defending the principle of sufficient reason sometimes described as the principle that nothing can be so without there being a reason why it is so. But the reason has to be of a particularly potent kind: eventually it has to ground contingent facts in necessities, and in particular in the reason an omnipotent and perfect being would have for actualizing one possibility than another. Among the consequences of the principle is Leibniz’s relational doctrine of space, since if space were an infinite box there could be no reason for the world to be at one point in rather than another, and God placing it at any point violate the principle. In Abelard’s (1079-1142), as in Leibniz, the principle eventually forces te recognition that the actual world is the best of all possibilities, since anything else would be inconsistent with the creative power that actualizes possibilities.

If truth consists in concept containment, then it seems that all truths are analytic and hence necessary; and if they are all necessary, surely they are all truths of reason. In that not every truth can be reduced to an identity in a finite number of steps; in some instances revealing the connection between subject and predicate concepts would require an infinite analysis, while this may entail that we cannot prove such proposition as a prior, it does not appear to show that proposition could have been false. Intuitively, it seems a better ground for supposing that it is a necessary truth of a special sort. A related question arises from the idea that truths of fact depend on God’s decision to create the best world: If it is part of the concept of this world that it is best, how could its existence be other than necessary? An accountable and responsively answered explanation would be so, that any relational question that brakes the norm lay eyes on its existence in the manner other than hypothetical necessities, i.e., it follows from God’s decision to create the world, but God had the power to create this world, but God is necessary, so how could he have decided to do anything else? Leibniz says much more about these matters, but it is not clear whether he offers any satisfactory solutions.

The view that the terms in which we think of some area are sufficiently infected with error for it to be better to abandon them than to continue to try to give coherent theories of their use. Eliminativism should be distinguished from scepticism that claims that we cannot know the truth about some area; eliminativism claims rather that there are no truth there to be known, in the terms that we currently think. An eliminativist about theology simply counsels abandoning the terms or discourse of theology, and that will include abandoning worries about the extent of theological knowledge.

Eliminativists in the philosophy of mind counsel abandoning the whole network of terms mind, consciousness, self, qualia that usher in the problems of mind and body. Sometimes the argument for doing this is that we should wait for a supposed future understanding of ourselves, based on cognitive science and better than any our current mental descriptions provide, sometimes it is supposed that physicalism shows that no mental description of ourselves could possibly be true.

Greek scepticism centred on the value of enquiry and questioning, scepticism is now the denial that knowledge or even rational belief is possible, either about some specific subject-matter, e.g., ethics, o r in any atra whatsoever. Classically, scepticism springs from the observation that the best methods in some area seem to fall short of giving us contact with the truth, e.g., there is a gulf between appearance and reality, and in frequency cites the conflicting judgements that our methods deliver, with the result that questions of truth become undecidable.

Sceptical tendencies emerged in the 14th-century writings of Nicholas of Autrecourt. His criticisms of any certainty beyond the immediate deliverance of the senses and basic logic, and in particular of any knowledge of either intellectual or material substances, anticipate the later scepticism of Balye and Hume. The; later distinguishes between Pyrrhonistic and excessive scepticism, which he regarded as unlivable, and the more mitigated scepticism that accepts every day or commonsense beliefs (not as the delivery of reason, but as due more to custom and habit), but is duly wary of the power of reason to give us much more. Mitigated scepticism is thus closer to the attitude fostered by ancient scepticism from Pyrrho through to Sexus Empiricus. Although the phrase ‘Cartesian scepticism’ is sometimes used, Descartes himself was not a sceptic, but in the method of doubt, uses a sceptical scenario in order to begin the process of finding a secure mark of knowledge. Descartes himself trusts a category of ‘clear and distinct’ ideas, not far removed from the phantasia kataleptiké of the Stoics.

Scepticism should not be confused with relativism, which is a doctrine about the nature of truth, and may be motivated by trying to avoid scepticism. Nor is it identical with eliminativism, which counsels abandoning an area of thought altogether, not because we cannot know the truth, but because there are no truths capable of being framed in the terms we use.

Descartes’s theory of knowledge starts with the quest for certainty, for an indubitable starting-point or foundation on the basis alone of which progress is possible. This is eventually found in the launching celebrations as gratified in the‘Cogito ergo sum’: I think: Therefore? I am. By locating the point of certainty in my own awareness of my own self, Descartes gives a first-person twist to the theory of knowledge that dominated them following centuries in spite of various counter-attacks on behalf of social and public starting-points. The metaphysical associated with this priority are the famous Cartesian dualism, or separation of mind and matter into two different but interacting substances, Descartes rigorously and rightly sees that it takes divine dispensation to certify any relationship between the two realms thus divided, and to prove the reliability of the senses invokes a ‘clear and distinct perception’ of highly dubious proofs of the existence of a benevolent deity. This has not met general acceptance: as Hume drily puts it, ‘to have recourse to the veracity of the supreme Being, in order to prove the veracity of our senses, is surely making a very unexpected circuit’.

In his own time Descartes’s conception of the entirely separate substance of the mind was recognized to give rise to insoluble problems of the nature of the causal connection between the two. It also gives rise to the problem, insoluble in its own terms, of other minds. Descartes’s notorious denial that non-human animals are conscious is a stark illustration of the problem. In his conception of matter Descartes also gives preference to rational cogitation over anything derived from the senses. Since we can conceive of the matter of a ball of wax surviving changes to its sensible qualities, matter is not an empirical concept, but eventually an entirely geometrical one, with extension and motion as its only physical nature. Descartes’s thought, as reflected in Leibniz, that the qualities of sense experience have no resemblance to qualities of things, so that knowledge of the external world is essentially knowledge of structure rather than of filling. On this basis Descartes erects a remarkable physics. Since matter is in effect the same as extension there can be no empty space or ‘void’, since there is no empty space motion is not a question of occupying previously empty space, but is to be thought of in terms of vortices (like the motion of a liquid).

Although the structure of Descartes’s epistemology, theories of mind, and theory of matter have been rejected many times, their relentless exposure of the hardest issues, their exemplary clarity, and even their initial plausibility, all contrives to make him the central point of reference for modern philosophy.

The self conceived as Descartes presents it in the first two Meditations: aware only of its own thoughts, and capable of disembodied existence, neither situated in a space nor surrounded by others. This is the pure self of ‘I-ness’ that we are tempted to imagine as a simple unique thing that make up our essential identity. Descartes’s view that he could keep hold of this nugget while doubting everything else is criticized by Lichtenberg and Kant, and most subsequent philosophers of mind.

Descartes holds that we do not have any knowledge of any empirical proposition about anything beyond the contents of our own minds. The reason, roughly put, is that there is a legitimate doubt about all such propositions because there is no way to deny justifiably that our senses are being stimulated by some cause (an evil spirit, for example) which is radically different from the objects that we normally think affect our senses.

He also points out, that the senses (sight, hearing, touch, etc., are often unreliable, and ‘it is prudent never to trust entirely those who have deceived us even once’, he cited such instances as the straight stick that looks ben t in water, and the square tower that look round from a distance. This argument of illusion, has not, on the whole, impressed commentators, and some of Descartes’ contemporaries pointing out that since such errors come to light as a result of further sensory information, it cannot be right to cast wholesale doubt on the evidence of the senses. But Descartes regarded the argument from illusion as only the first stage in softening up process which would ‘lead the mind away from the senses’. He admits that there are some cases of sense-base belief about which doubt would be insane, e.g., the belief that I am sitting here by the fire, wearing a winter dressing gown’.

Descartes was to realize that there was nothing in this view of nature that could explain or provide a foundation for the mental, or from direct experience as distinctly human. In a mechanistic universe, he said, there is no privileged place or function for mind, and the separation between mind and matter is absolute. Descartes was also convinced, that the immaterial essences that gave form and structure to this universe were coded in geometrical and mathematical ideas, and this insight led him to invent algebraic geometry.

A scientific understanding of these ideas could be derived, said Descartes, with the aid of precise deduction, and he also claimed that the contours of physical reality could be laid out in three-dimensional coordinates. Following the publication of Newton’s Principia Mathematica in 1687, reductionism and mathematical modelling became the most powerful tools of modern science. And the dream that the entire physical world could be known and mastered through the extension and refinement of mathematical theory became the central feature and guiding principle of scientific knowledge.

Having to its recourse of knowledge, its cental questions include the origin of knowledge, the place of experience in generating knowledge, and the place of reason in doing so, the relationship between knowledge and certainty, and between knowledge and the impossibility of error, the possibility of universal scepticism, and the changing forms of knowledge that arise from new conceptualizations of the world. All of these issues link with other central concerns of philosophy, such as the nature of truth and the natures of experience and meaning.

Foundationalism was associated with the ancient Stoics, and in the modern era with Descartes (1596-1650). Who discovered his foundations in the ‘clear and distinct’ ideas of reason? Its main opponent is Coherentism, or the view that a body of propositions mas be known without a foundation in certainty, but by their interlocking strength, than as a crossword puzzle may be known to have been solved correctly even if each answer, taken individually, admits of uncertainty. Difficulties at this point led the logical passivists to abandon the notion of an epistemological foundation altogether, and to flirt with the coherence theory of truth. It is widely accepted that trying to make the connection between thought and experience through basic sentences depends on an untenable ‘myth of the given’.

Still in spite of these concerns, the problem, least of mention, is of defining knowledge in terms of true beliefs plus some favoured relations between the believer and the facts that began with Plato’s view in the “Theaetetus,” that knowledge is true belief, and some logos. Due of its nonsynthetic epistemology, the enterprising of studying the actual formation of knowledge by human beings, without aspiring to certify those processes as rational, or its proof against ‘scepticism’ or even apt to yield the truth. Natural epistemology would therefore blend into the psychology of learning and the study of episodes in the history of science. The scope for ‘external’ or philosophical reflection of the kind that might result in scepticism or its refutation is markedly diminished. Despite the fact that the terms of modernity are so distinguished as exponents of the approach include Aristotle, Hume, and J. S. Mills.

The task of the philosopher of a discipline would then be to reveal the correct method and to unmask counterfeits. Although this belief lay behind much positivist philosophy of science, few philosophers now subscribe to it. It places too well a confidence in the possibility of a purely previous ‘first philosophy’, or viewpoint beyond that of the work one’s way of practitioners, from which their best efforts can be measured as good or bad. These standpoints now seem that too many philosophers to be a fanciefancy, that the more modest of tasks that are actually adopted at various historical stages of investigation into different areas with the aim not so much of criticizing but more of systematization, in the presuppositions of a particular field at a particular tie. There is still a role for local methodological disputes within the community investigators of some phenomenon, with one approach charging that another is unsound or unscientific, but logic and philosophy will not, on the modern view, provide an independent arsenal of weapons for such battles, which indeed often come to seem more like political bids for ascendancy within a discipline.

This is an approach to the theory of knowledge that sees an important connection between the growth of knowledge and biological evolution. An evolutionary epistemologist claims that the development of human knowledge processed through some natural selection process, the best example of which is Darwin’s theory of biological natural selection. There is a widespread misconception that evolution proceeds according to some plan or direct, but it has neither, and the role of chance ensures that its future course will be unpredictable. Random variations in individual organisms create tiny differences in their Darwinian fitness. Some individuals have more offsprings than others, and the characteristics that increased their fitness thereby become more prevalent in future generations. Once upon a time, at least a mutation occurred in a human population in tropical Africa that changed the haemoglobin molecule in a way that provided resistance to malaria. This enormous advantage caused the new gene to spread, with the unfortunate consequence that sickle-cell anaemia came to exist.

Chance can influence the outcome at each stage: First, in the creation of genetic mutation, second, in wether the bearer lives long enough to show its effects, thirdly, in chance events that influence the individual’s actual reproductive success, and fourth, in whether a gene even if favoured in one generation, is, happenstance, eliminated in the next, and finally in the many unpredictable environmental changes that will undoubtedly occur in the history of any group of organisms. As Harvard biologist Stephen Jay Gould has so vividly expressed that process over again, the outcome would surely be different. Not only might there not be humans, there might not even be anything like mammals.

We will often emphasis the elegance of traits shaped by natural selection, but the common idea that nature creates perfection needs to be analysed carefully. The extent to which evolution achieves perfection depends on exactly what you mean. If you mean “Does natural selections always take the best path for the long-term welfare of a species?” The answer is no. That would require adaption by group selection, and this is, unlikely. If you mean “Does natural selection creates every adaption that would be valuable?” The answer again, is no. For instance, some kinds of South American monkeys can grasp branches with their tails. The trick would surely also be useful to some African species, but, simply because of bad luck, none have it. Some combination of circumstances started some ancestral South American monkeys using their tails in ways that ultimately led to an ability to grab onto branches, while no such development took place in Africa. Mere usefulness of a trait does not necessitate a means in that what will understandably endure phylogenesis or evolution.

This is an approach to the theory of knowledge that sees an important connection between the growth of knowledge and biological evolution. An evolutionary epistemologist claims that the development of human knowledge proceeds through some natural selection process, the best example of which is Darwin’s theory of biological natural selection. The three major components of the model of natural selection are variation selection and retention. According to Darwin’s theory of natural selection, variations are not pre-designed to do certain functions. Rather, these variations that do useful functions are selected. While those that do not employ of some coordinates in that are regainfully purposed are also, not to any of a selection, as duly influenced of such a selection, that may have responsibilities for the visual aspects of a variational intentionally occurs. In the modern theory of evolution, genetic mutations provide the blind variations: Blind in the sense that variations are not influenced by the effects they would have-the likelihood of a mutation is not correlated with the benefits or liabilities that mutation would confer on the organism, the environment provides the filter of selection, and reproduction provides the retention. Fatnesses are achieved because those organisms with features that make them less adapted for survival do not survive in connection with other organisms in the environment that have features that are better adapted. Evolutionary epistemology applies this blind variation and selective retention model to the growth of scientific knowledge and to human thought processes overall.

The parallel between biological evolution and conceptual or ‘epistemic’ evolution can be seen as either literal or analogical. The literal version of evolutionary epistemology deeds biological evolution as the main cause of the growth of knowledge. On this view, called the ‘evolution of cognitive mechanic programs’, by Bradie (1986) and the ‘Darwinian approach to epistemology’ by Ruse (1986), that growth of knowledge occurs through blind variation and selective retention because biological natural selection itself is the cause of epistemic variation and selection. The most plausible version of the literal view does not hold that all human beliefs are innate but rather than the mental mechanisms that guide the acquisitions of non-innate beliefs are themselves innately and the result of biological natural selection. Ruse, (1986) demands of a version of literal evolutionary epistemology that he links to sociolology (Rescher, 1990).

On the analogical version of evolutionary epistemology, called the ‘evolution of theory’s program’, by Bradie (1986). The ‘Spenserians approach’ (after the nineteenth century philosopher Herbert Spencer) by Ruse (1986), the development of human knowledge is governed by a process analogous to biological natural selection, rather than by an instance of the mechanism itself. This version of evolutionary epistemology, introduced and elaborated by Donald Campbell (1974) as well as Karl Popper, sees the [partial] fit between theories and the world as explained by a mental process of trial and error known as epistemic natural selection.

Both versions of evolutionary epistemology are usually taken to be types of naturalized epistemology, because both take some empirical facts as a starting point for their epistemological project. The literal version of evolutionary epistemology begins by accepting evolutionary theory and a materialist approach to the mind and, from these, constructs an account of knowledge and its developments. In contrast, the metaphorical version does not require the truth of biological evolution: It simply draws on biological evolution as a source for the model of natural selection. For this version of evolutionary epistemology to be true, the model of natural selection need only apply to the growth of knowledge, not to the origin and development of species. Crudely put, evolutionary epistemology of the analogical sort could still be true even if Creationism is the correct theory of the origin of species.

Although they do not begin by assuming evolutionary theory, most analogical evolutionary epistemologists are naturalized epistemologists as well, their empirical assumptions, least of mention, implicitly come from psychology and cognitive science, not evolutionary theory. Sometimes, however, evolutionary epistemology is characterized in a seemingly non-naturalistic fashion. Campbell (1974) says that ‘if one is expanding knowledge beyond what one knows, one has no choice but to explore without the benefit of wisdom’, i.e., blindly. This, Campbell admits, makes evolutionary epistemology close to being a tautology (and so not naturalistic). Evolutionary epistemology does assert the analytic claim that when expanding one’s knowledge beyond what one knows, one must precessed to something that is already known, but, more interestingly, it also makes the synthetic claim that when expanding one’s knowledge beyond what one knows, one must proceed by blind variation and selective retention. This claim is synthetic because it can be empirically falsified. The central claim of evolutionary epistemology is synthetic, not analytic. If the central contradictory, which they are not. Campbell is right that evolutionary epistemology does have the analytic feature he mentions, but he is wrong to think that this is a distinguishing feature, since any plausible epistemology has the same analytic feature (Skagestad, 1978).

Two extraordinary issues lie to awaken the literature that involves questions about ‘realism’, i.e., What metaphysical commitment does an evolutionary epistemologist have to make? Progress, i.e., according to evolutionary epistemology, does knowledge develop toward a goal? With respect to realism, many evolutionary epistemologists endorse that is called ‘hypothetical realism’, a view that combines a version of epistemological ‘scepticism’ and tentative acceptance of metaphysical realism. With respect to progress, the problem is that biological evolution is not goal-directed, but the growth of human knowledge seems to be. Campbell (1974) worries about the potential dis-analogy here but is willing to bite the stone of conscience and admit that epistemic evolution progress toward a goal (truth) while biologic evolution does not. Many another has argued that evolutionary epistemologists must give up the ‘truth-topic’ sense of progress because a natural selection model is in essence, is non-teleological, as an alternative, following Kuhn (1970), and embraced in the accompaniment with evolutionary epistemology.

Among the most frequent and serious criticisms levelled against evolutionary epistemology is that the analogical version of the view is false because epistemic variation is not blind (Skagestad, 1978, 613-16, and Ruse, 1986, ch.2 (. Stein and Lipton (1990) have argued, however, that this objection fails because, while epistemic variation is not random, its constraints come from heuristics that, for the most part, are selective retention. Further, Stein and Lipton come to the conclusion that heuristics are analogous to biological pre-adaptions, evolutionary pre-biological pre-adaptions, evolutionary cursors, such as a half-wing, a precursor to a wing, which have some function other than the function of their descendable structures: The function of descendable structures, the function of their descendable character embodied to its structural foundations, is that of the guidelines of epistemic variation is, on this view, not the source of disanalogousness, but the source of a more articulated account of the analology.

Many evolutionary epistemologists try to combine the literal and the analogical versions (Bradie, 1986, and Stein and Lipton, 1990), saying that those beliefs and cognitive mechanisms, which are innate results from natural selection of the biological sort and those that are innate results from natural selection of the epistemic sort. This is reasonable as long as the two parts of this hybrid view are kept distinct. An analogical version of evolutionary epistemology with biological variation as its only source of blondeness would be a null theory: This would be the case if all our beliefs are innate or if our non-innate beliefs are not the result of blind variation. An appeal to the legitimate way to produce a hybrid version of evolutionary epistemology since doing so trivializes the theory. For similar reasons, such an appeal will not save an analogical version of evolutionary epistemology from arguments to the effect that epistemic variation is blind (Stein and Lipton, 1990).

Although it is a new approach to theory of knowledge, evolutionary epistemology has attracted much attention, primarily because it represents a serious attempt to flesh out a naturalized epistemology by drawing on several disciplines. In science is relevant to understanding the nature and development of knowledge, then evolutionary theory is among the disciplines worth a look. Insofar as evolutionary epistemology looks there, it is an interesting and potentially fruitful epistemological programme.

What makes a belief justified and what makes a true belief knowledge? Thinking that whether a belief deserves one of these appraisals is natural depends on what caused the depicted branch of knowledge to have the belief. In recent decades a number of epistemologists have pursued this plausible idea with a variety of specific proposals. Some causal theories of knowledge have it that a true belief that ‘p’ is knowledge just in case it has the right causal connection to the fact that ‘p’. Such a criterion can be applied only to cases where the fact that ‘p’ is a sort that can enter into causal relations, as this seems to exclude mathematically and the necessary facts and perhaps any fact expressed by a universal generalization, and proponents of this sort of criterion have usually supposed that it is limited to perceptual representations where knowledge of particular facts about subjects’ environments.

For example, Armstrong (1973), predetermined that a position held by a belief in the form ‘This perceived object is ‘F’ is [non-inferential] knowledge if and only if the belief is a completely reliable sign that the perceived object is ‘F’, that is, the fact that the object is ‘F’ contributed to causing the belief and its doing so depended on properties of the believer such that the laws of nature dictated that, for any subject ‘χ’ and perceived object ‘y’, if ‘χ’ has those properties and believed that ‘y’ is ‘F’, then ‘y’ is ‘F’. (Dretske (1981) offers a rather similar account, in terms of the belief’s being caused by a signal received by the perceiver that carries the information that the object is ‘F’).

Goldman (1986) has proposed an importantly different causal criterion, namely, that a true belief is knowledge if it is produced by a type of process that is ‘globally’ and ‘locally’ reliable. Causing true beliefs is sufficiently high is globally reliable if its propensity. Local reliability has to do with whether the process would have produced a similar but false belief in certain counterfactual situations alternative to the actual situation. This way of marking off true beliefs that are knowledge does not require the fact believed to be causally related to the belief, and so it could in principle apply to knowledge of any kind of truth.

Goldman requires the global reliability of the belief-producing process for the justification of a belief, he requires it also for knowledge because justification is required for knowledge. What he requires for knowledge, but does not require for justification is local reliability. His idea is that a justified true belief is knowledge if the type of process that produced it would not have produced it in any relevant counterfactual situation in which it is false. Its purported theory of relevant alternatives can be viewed as an attempt to provide a more satisfactory response to this tension in our thinking about knowledge. It attempts to characterize knowledge in a way that preserves both our belief that knowledge is an absolute concept and our belief that we have knowledge.

According to the theory, we need to qualify rather than deny the absolute character of knowledge. We should view knowledge as absolute, reactive to certain standards (Dretske, 1981 and Cohen, 1988). That is to say, in order to know a proposition, our evidence need not eliminate all the alternatives to that preposition, rather for ‘us’, that we can know our evidence eliminates al the relevant alternatives, where the set of relevant alternatives (a proper subset of the set of all alternatives) is determined by some standard. Moreover, according to the relevant alternatives view, and the standards determining that of the alternatives is raised by the sceptic are not relevant. If this is correct, then the fact that our evidence cannot eliminate the sceptic’s alternative does not lead to a sceptical result. For knowledge requires only the elimination of the relevant alternatives, so the relevant alternative view preserves in both strands in our thinking about knowledge. Knowledge is an absolute concept, but because the absoluteness is relative to a standard, we can know many things.