western philosophy 4101

Western Philosophy

April 29, 2021

Western Philosophy (Greek philosophia, “love of wisdom”), the rational and critical inquiry into basic principles. Philosophy is often divided into four main branches: metaphysics, the investigation of ultimate reality; epistemology, the study of the origins, validity, and limits of knowledge; ethics, the study of the nature of morality and judgment; and aesthetics, the study of the nature of beauty in the fine arts.

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, see Chinese Philosophy; Islam; Buddhism; Daoism (Taoism); Confucianism; Indian Philosophy.


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.

A The Ionian School

The first philosopher of historical record was Thales, who lived in the 6th century bc in Miletus, a city 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.

In general, 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.

B The Pythagorean School

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 practicing 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.

C The Heraclitean School

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.)

D The Eleatic School

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.

E The Pluralists

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.

F The Atomists

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 infinitely divisible but is composed of numerous indivisible particles that are too small for human senses to detect. His conception of nature was thoroughly materialistic (focused 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 odor, 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.

G The Sophists

Toward the end of the 5th century bc, a group of traveling 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.

H Socratic Philosophy

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.

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.

I Platonic Philosophy

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.

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.

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 behavior 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.

J Aristotelian Philosophy

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 became 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 centers 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 soul is 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 behavior, 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 fulfillment 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 (see Criticism, Literary).


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 schools 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.

A Epicureanism

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.

B Stoicism

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 tranquility 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 worshiping 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.

C Skepticism

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 skillfully. 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 tranquility and fulfillment. 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.

D Neoplatonism

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; 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.

A Augustinian Philosophy

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.

The 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 expressed 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.

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 treeness 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.

B Scholasticism

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 labors established the foundations of Scholasticism.

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 and combined Platonism with Christian theology. Supporting the Platonic theory of Ideas, Anselm argued in favor 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.

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 an ethics based on personal conscience that anticipated Protestant thought.

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.

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.

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 worshiped 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.

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 (see Deduction).

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.

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.

C Medieval Philosophy After Aquinas

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 center 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 worldview.

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.

A Mechanism and Materialism

In the new philosophical climate, experience and reason became the sole standards of truth. The first great spokesman 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).

The work of Italian physicist and astronomer Galileo was of even greater importance in the development of a new worldview. 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.

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.

A1 Descartes

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.

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.

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 that has remained a concern of philosophy ever since. 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.

A2 Hobbes

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.

In his ethical theory Hobbes derived the rules of human behavior 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.

A3 Spinoza

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 body 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).

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 a 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.

A4 Locke

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 to rigorously 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 centuries. 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 defense 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.

B Idealism and Skepticism

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 skeptical 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.

B1 Leibniz

German philosopher Gottfried Wilhelm Leibniz, like Spinoza before him, worked in the rationalist (reason-based) tradition to produce a brilliant solution to the problems raised by dualism. Leibniz, a mathematician and statesman as well as a philosopher, developed a remarkably subtle and original system of philosophy that combined the mathematical and physical discoveries of his time with the organic and religious conceptions of nature found in ancient and medieval thought. Leibniz viewed the world as an infinite number of infinitely small units of force, called monads, each of which is a closed world but mirrors all the other monads through its activity, which is perception. All the monads are spiritual entities, but they can combine to form material bodies. Leibniz conceived of God as the Monad of Monads, which creates all other monads and predestines their development.

Leibniz’s theory of the predestination of monads, also called the theory of preestablished harmony, entailed a radical rejection of causality—the view that every effect must have a cause. According to Leibniz, monads do not interact with each other at all, and the appearance of mechanical causality in the natural world is unreal, akin to an illusion. Likewise, there is no room in the universe for free will: Even though we enjoy the illusion of acting freely, all human actions are predetermined by God. Despite these gloomy conclusions, Leibniz’s philosophy was profoundly optimistic because he argued that ours was the best of all possible worlds. He based this belief on considerations about the nature of truth and necessity. French writer Voltaire mocked this viewpoint in Candide (1759), a satirical novel that examines the woes heaped on the world in the name of God.

B2 Berkeley

In the 18th century Irish philosopher and Anglican churchman George Berkeley, like Spinoza before him, rejected both Cartesian dualism and the assertion by Hobbes that only matter is real. Berkeley maintained that spirit is substance, and that only spiritual substance is real. Extending Locke’s doubts about knowledge of an external world, outside the mind, Berkeley argued that no evidence exists for the existence of such a world, because the only things that we can observe are our own sensations, and these are in the mind. The very notion of matter, he maintained, is incoherent and impossible. To exist, he claimed, means to be perceived (“esse est percipi”), and in order for things to exist when we are not observing them, they must continue to be perceived by God. By claiming that sensory phenomena are the only objects of human knowledge, Berkeley established the view known as phenomenalism, a theory of perception that suggests that matter can be analyzed in terms of sensations.

B3 Hume

Whereas Berkeley argued against materialism by denying the existence of matter, 18th-century Scottish philosopher David Hume questioned the existence of the mind itself. Hume’s skeptical philosophy also cast doubt on the idea of cause as understood in all previous philosophies and seriously disputed earlier arguments for the existence of God. His most important philosophical work, A Treatise of Human Nature, was published in three volumes in 1739 and 1740.

All metaphysical assertions about things that cannot be directly perceived are equally meaningless, Hume claimed, and should be “committed to the flames.” In his analyses of causality and induction, Hume revealed that there is no logical justification for believing that any two events which occur together are connected by cause and effect or for making any inference from past to future. Hume noted that we depend on our past experience whenever we form beliefs about anything that we do not directly perceive and whenever we make predictions about the future. According to the empiricist doctrine of Bacon, Locke, and Berkeley, we can do this because experience teaches us what particular things belong together as causes and effects. Hume, however, argued that this attempt to learn from experience is not at all rational, thus calling into question the reliability of our memories, our reasoning processes, and our ability to learn from past experiences or to make even the smallest predictions about the future—for example, that the sun will rise tomorrow. Though extreme, Hume’s skepticism about philosophical empiricism raised problems about the possibility of knowledge that contemporary philosophers still struggle to resolve.

B4 Kant

German philosopher Immanuel Kant was among the first to appreciate Hume’s skepticism, and in response he published the Critique of Pure Reason (1781), widely considered the greatest single work in modern philosophy. In this work Kant made a thorough and systematic analysis of the conditions for knowledge. As an example of genuine knowledge, he had in mind the contributions to physics of English scientist Isaac Newton. In the case of Newtonian physics, reason seemed to have done an effective job of understanding the data supplied by the senses and to have succeeded in postulating universal and necessary laws of nature, such as the law of gravitation and the laws of motion. Kant proposed to explain how such knowledge is possible, thereby providing a complete reply to Hume’s skepticism and answering many of the problems that had plagued Western philosophers since the time of Descartes.

Kant started by making a fresh analysis of the elements of knowledge, asking for the first time an extremely basic question, “How is our experience possible in the first place?” Kant’s predecessors had taken experience for granted. Thus Descartes agreed that we seem to have sensory knowledge of the world but asked whether this knowledge was true or the result of a dream. Similarly, Hume’s skepticism about causation arose when he concluded that we do not encounter causality in our ordinary experience of the world and that any inferences about it, beyond immediate experience, were questionable. Kant’s answer to the skepticism of Descartes and Hume involved certain categories, such as space, time, substance, and causality, which he maintained are essential to our thinking and to our experience of phenomena in the world. These categories he called transcendental. All objects of our knowledge, he concluded, must conform to the human mind’s essential ways of perceiving and understanding—ways that involve the transcendental categories—if they are to be knowable at all. Kant maintained that he had developed a revolutionary hypothesis about knowledge and reality that he believed to be as significant for the future of philosophy as the hypothesis of Copernicus—that the planets orbit the Sun—had been for science.

Kant’s claim that causality, substance, space, and time are forms imposed by the mind gave support to the idealism of Leibniz and Berkeley. Kant, however, made his view a more critical form of idealism by granting the empiricist claim that things-in-themselves—that is, things as they exist outside human experience—are unknowable. Kant therefore limited knowledge to the “phenomenal world” of experience, maintaining that metaphysical beliefs about the soul, the cosmos, and God (the “noumenal world” transcending human experience) are matters of faith rather than of scientific knowledge.

In his ethical writings Kant held that moral principles are categorical imperatives, absolute commands of reason that permit no exceptions and are not related to pleasure or practical benefit. Kant argued that human beings should act as members of an ideal “kingdom of ends” in which every person is treated as an end in himself or herself, and never as a means to someone else’s ends. In addition, everyone should govern their conduct as if their actions were to be made law—a law that applies equally to all without exception. Kant thereby postulated a freedom of action based on moral order and equality. His moral philosophy contributed to modern political ideas about freedom and democracy. Kant was a leading figure of the movement for reason and liberty against tradition and authority, and in his religious teachings he emphasized individual conscience and represented God primarily as a moral ideal.

Kant’s writings constituted a high point of the Enlightenment, a fertile intellectual and cultural period that helped stimulate the social changes that produced the French Revolution (1789-1799). Other leading thinkers of this movement included Voltaire, Jean Jacques Rousseau, and Denis Diderot. Voltaire, developing the tradition of Deism begun by Locke and other liberal thinkers, reduced religious beliefs to those that can be justified by rational inference from the study of nature. Rousseau criticized civilization as a corruption of humanity’s nature and developed Hobbes’s doctrine that the state is based on a social contract with its citizens and represents the popular will. Diderot published a 35-volume work known as the Encyclopédie to which many scientists and philosophers contributed. Diderot and his Encyclopedists, as they were known, associated the progress and the happiness of humankind with science and knowledge, whereas Rousseau criticized such ideas along with the very notion of civilization.

C 19th-Century Philosophy

Philosophers of the 19th century generally developed their views with reference to the work of Kant. In Germany, Kant’s influence led subsequent philosophers to explore idealism and ethical voluntarism, a philosophical tradition that places a strong emphasis on human will. Whereas philosophers before Kant had explored the objects of knowledge, German philosophers who followed Kant on the path of idealism turned to the subject of knowledge—known variously as the ego, the I, the mind, and human consciousness.

Johann Gottlieb Fichte transformed Kant’s critical idealism into absolute idealism by eliminating Kant’s “things-in-themselves” (external reality) and making the self, or the ego, the ultimate reality. Fichte maintained that the world is created by an absolute ego, which is conscious first of itself and only later of non-self, or the otherness of the world. The human will, a partial manifestation of self, gives human beings freedom to act. Friedrich Wilhelm Joseph von Schelling moved still further toward absolute idealism by construing objects or things as the works of the imagination and Nature as an all-embracing being, spiritual in character. Schelling became the leading philosopher of the movement known as romanticism, which in contrast to the Enlightenment placed its faith in feeling and the creative imagination rather than in reason. The romantic view of the divinity of nature influenced the American transcendentalist movement, led by poet and essayist Ralph Waldo Emerson.

C1 Hegel

The most powerful philosophical mind of the 19th century was the German philosopher Georg Wilhelm Friedrich Hegel, whose system of absolute idealism, although influenced greatly by Kant and Schelling, was based on a new conception of logic and philosophical method. Hegel believed that absolute truth, or reality, exists and that the human mind can know it. This is so because “whatever is real is rational,” according to Hegel. He conceived the subject matter of philosophy to be reality as a whole, a reality that he referred to as Absolute Spirit, or cosmic reason. The world of human experience, whether subjective or objective, he viewed as the manifestation of Absolute Spirit.

Philosophy’s task, according to Hegel, is to chart the development of Absolute Spirit from abstract, undifferentiated being into more and more concrete reality. Hegel believed this development occurs by a dialectical process—that is, a process through which conflicting ideas become resolved—which consists of a series of stages that occur in triads (sets of three). Each triad involves (1) an initial state (or thesis), which might be an idea or a movement; (2) its opposite state (or antithesis); and (3) a higher state, or synthesis, that combines elements from the two opposites into a new and superior arrangement. The synthesis then becomes the thesis of the next triad in an unending progress toward the ideal.

Hegel argued that this dialectical logic applies to all knowledge, including science and history. His discussion of history was particularly influential, especially because it supported the political and social philosophy later developed by Karl Marx. According to Hegel human history demonstrates the dialectical development of Absolute Spirit, which can be observed by studying conflicts and wars and the rise and fall of civilizations. He maintained that political states are real entities, the manifestation of Spirit in the world, and participants of history. In every epoch a particular state is the bearer or agent of spiritual advance, and it thereby gathers to itself power. Because the dialectic means opposition and conflict, war must be expected, and it has value as evidence of the health of a state.

Hegel’s philosophy stimulated interest in history by representing it as a deeper penetration into reality than the natural sciences provide. His conception of the national state as the highest social embodiment of the Absolute Spirit was for some time believed to be a main source of 20th-century totalitarianism, although Hegel himself advocated a large measure of individual freedom.

C2 Schopenhauer

German philosophers of the 19th century who came after Hegel rejected Hegel’s faith in reason and progress. Arthur Schopenhauer in The World as Will and Idea (1819) argued that existence is fundamentally irrational and an expression of a blind, meaningless force—the human will, which encompasses the will to live, the will to reproduce, and so forth. Will, however, entails continuous striving and results in disappointment and suffering. Schopenhauer offered two avenues of escape from irrational will: through the contemplation of art, which enables one to endure the tragedy of life, and through the renunciation of will and of the striving for happiness.

Schopenhauer was one of the first Western philosophers to be influenced by Indian philosophy, which was then appearing in Europe in translation. The influence of Buddhist thought, for example, appears in his sense that the world is full of evil and suffering which can be overcome only through resignation and renunciation. Schopenhauer’s own view that an irrational force lies at the center of life subsequently influenced voluntaristic psychology, a school of psychology that emphasized the causes for our choices; sociological studies that examine nonrational factors affecting people; and cultural attitudes that play down the value of reason in life.

C3 Nietzsche

German philosopher Friedrich Nietzsche continued the revolt against reason initiated by the romantic movement, but he scornfully repudiated Schopenhauer’s negative, resigned attitude. Instead, Nietzsche affirmed the value of vitality, strength, and the supremacy of an existence that is purely egoistic. He also scorned the Christian and democratic ideas of the equal worth of human beings, maintaining that it is up to a few aristocrats to refuse to subordinate themselves to a state or cause, and thereby achieve self-realization and greatness. For Nietzsche the power to be strong was the greatest value in life. Although Nietzsche valued geniuses over dictators, his beliefs helped bolster the ideas of the National Socialists (Nazis) who gained control of Germany in the 1930s (see National Socialism).

C4 Kierkegaard

Danish philosopher Søren Kierkegaard developed another distinctive philosophy of life. Kierkegaard’s ideas, which were not appreciated until a century after their appearance, were literary, religious, and self-revealing rather than systematic in character. They stressed the importance of experiences that the intellectual mind judges as absurd, including the experiences of angst (“anxiety”) and “fear and trembling.” (The latter phrase is the title of one of his books.) Such experiences, in his view, lead first to despair and eventually to religious faith. Kierkegaard discussed this process in terms of the religious person who is commanded by God to sacrifice his own most cherished treasures, as in the example of Abraham and the sacrifice of Isaac in the Old Testament. Although Abraham cannot understand this absurd request from God, he decides to obey his commitment to God. Through such terrible experiences, Kierkegaard claimed, we learn that humanity’s relationship to God is absolute and all else relative. What is most significant in a person’s life, Kierkegaard concluded, are the decisions made in such ethical crises.

Kierkegaard’s ideas came to have importance in the 20th century. The concepts of existence, dread, the absurd, and decision were influential in Germany, France, and English-speaking countries. The condition of humankind during an epoch with two world wars gave these ideas a new relevance; the philosophers who developed them founded the movement now known as existentialism.

C5 Bentham and Mill

Jeremy Bentham and John Stuart Mill, both economists as well as philosophers, dominated philosophy in England during the 19th century. Bentham originated the ethical principle of utilitarianism—that what is useful is good—and Mill developed and refined the doctrine. The utilitarians argued for an ethical principle that would be superior to the self-interest of the individual, just as Kant had established a rational principle of moral law superior to individual desire, by which people’s conduct ought to be governed. The utilitarians based their principle on the theory that everyone desires his or her own happiness, that people have to find that happiness in society, and that consequently we all have an interest in the general happiness. They took the position that whatever produces the greatest happiness for the greatest number of people is what is most useful for all. This is the meaning of the principle of utility, or benefit, from which utilitarianism takes its name.

In evaluating happiness, Bentham believed it possible to measure quantitatively the pleasures resulting from each action—the pleasures of oneself and the pleasure of others—and thus to decide in any instance what promoted the greatest amount of happiness. Mill partly abandoned that idea and maintained that one should consider the quality, or type, of pleasure as well as the quantity. Mill applied utilitarian principles to social justice, and the principle of utility influenced legislation that brought about social and economic reforms in Great Britain.

C6 Karl Marx and Marxism

The most influential achievement in political philosophy during the 19th century was the development of Marxism (see Political Theory). German political philosopher Karl Marx, who created the system known as Marxism, and his collaborator Friedrich Engels accepted the basic form of Hegel’s dialectic of history, but they made crucial modifications. For them history was a matter of the development not of Absolute Spirit but of the material conditions governing humanity’s economic existence. In their view, later known as historical materialism, the history of society is a history of class struggle in which the ruling class uses religion and other traditions and institutions, as well as its economic power, to reinforce its domination over the working classes. Human culture, according to Marx, is dependent on economic (material) conditions and serves economic ends. Religion, he concluded, is “the opiate of the masses” that serves the political end of suppressing mass revolution. Marxism is a theory of revolution, of history, of economics, and of politics, and it served as the ideology for Communism. Although he was a philosopher Marx had disdain for merely theoretical intellectual work, stating, “The philosophers have only interpreted the world in different ways; the point is to change it.”

Marx’s view of human history is both profoundly pessimistic and profoundly optimistic. Its pessimism lies in his belief that history reflects the oppression of the many by a small minority, who thereby secure economic and political power. It is optimistic on two counts. First, Marx believed that technical innovations bring about new ways of meeting human needs and make it increasingly possible for people to satisfy their deepest wants and to develop and perfect their individual capacities. Second, Marx claimed to have proved that the long history of oppression would soon end when the masses rise up and usher in a revolution that will create a classless utopian society. The first idea enabled Marx to bring attention in the modern era to Aristotle’s idealistic conception of human flourishing, which called upon people to develop and manifest many different abilities, including intellectual, artistic, and physical skills. The second idea motivated much radical activity during the 20th century, including the Russian Revolutions of 1917, the Communist victory in China in 1949, and the Cuban Revolution of 1959.

C7 Pragmatism

Toward the end of the 19th century, pragmatism became the most vital school of thought within American philosophy. It continued the empiricist tradition of grounding knowledge on experience and stressing the inductive procedures of experimental science. The pragmatists believed in the progress of human knowledge and that ideas are tools whose validity and significance are established as people adapt and test them in physical and social settings. For pragmatists, ideas demonstrate their value insofar as they enrich human experience.

The three most important American philosophers of the pragmatic movement were Charles Sanders Peirce, who founded pragmatism and gave the movement its name; psychologist and religious thinker William James; and psychologist and educator John Dewey. Their work continued into the 20th century. Peirce formulated a pragmatic theory of knowledge and advocated “laboratory philosophy” whereby researchers investigate and clarify the kinds of knowledge that can be gained either through everyday experience or through scientific inquiry. By limiting the realm of meaningful questions to those that concern possible experience, Peirce hoped to introduce scientific logic into metaphysics. He advanced a theory of truth that defined truth as that which an ideal community of researchers could agree upon. Peirce concluded that many traditional philosophical concepts have no practical use and thus are meaningless.

Whereas Peirce sought to determine the meaning of terms and ideas and thereby make metaphysics a precise and pragmatic discipline, James and Dewey applied the principles of pragmatism in developing a comprehensive philosophy. Like Peirce, James maintained that the meaning of ideas lies in their practical consequences. If an idea has no practical uses, then it is meaningless. James focused on the power of true ideas to offer individuals, rather than scientific researchers, practical guidance in handling problems that arise in everyday experience. Truth, according to James, resides in those experiences that enable people to successfully navigate the challenges and demands of the world.

Dewey emphasized the cooperative process in which human beings, as intelligent and social beings, create and revise ideas about the world. One such process was scientific inquiry; another was participation in just and democratic social and political communities. Dewey concluded that science and democracy are the only sure guides for intelligent behavior. His progressive social philosophy communicates a vision of a world in which science, education, and social reform demonstrate the benefits of pragmatic ideas for human life.

D 20th-Century Philosophy

A diversity of methods, interests, and styles of argumentation marked 20th-century philosophy and proved both fruitful and destructive. This diversity, and the divisions that arose, proved fruitful as new topics arose and new ways developed for discussing these topics philosophically. It proved destructive, however, as philosophers wrote increasingly for a narrow audience and often ignored or derided philosophical styles different from their own.

In the decades following World War II (1939-1945), significant divisions arose between so-called continental philosophers, who worked on the European continent, and philosophers in the United States, the United Kingdom, and Australia. Deconstruction and other postmodern theories followed existentialism and phenomenology on the continent, whereas the Americans, Britons, and Australians worked in the analytic tradition. In the final decades of the century, the divisions between continental and analytic philosophy eased as interest moved away from the old disputes, and more and more philosophers became interested in exploring common roots of the two traditions in the history of Western philosophy.

D1 Phenomenology

German philosopher Edmund Husserl founded the 20th-century movement of phenomenology. Husserl said that philosophers must attempt to describe and analyze phenomena as they occur, setting aside such considerations as whether the phenomena are objective or subjective. He emphasized careful observation and interpretation of our conscious perceptions of things. First, we must attend to what we are conscious of, observing our perceptions far more carefully and intensely than we do in everyday life. Second, we must reflect upon these observations and interpret them without preconceptions. Husserl maintained that we arrive at meaning and the key to solving philosophical problems through a logical analysis of the data that emerges from such a “phenomenological study” of the contents of the mind.

French philosopher Maurice Merleau-Ponty and German philosopher Martin Heidegger further developed phenomenology and its emphasis on pure description. For Merleau-Ponty, however, all perceptual experience carries with it a reference to something beyond and independent of our perception of it. Heidegger, too, sought to return to what he claimed had become unfamiliar—Sein (German for “being” or “existence”).

D2 Existentialism

Heidegger was also a key figure in the 20th-century movement known as existentialism. Existentialists focused on the personal: on individual existence, subjectivity, and choice. Two central existential doctrines claim that there is no fixed human essence structuring our lives and that our choices are never determined by anything except our own free will. In making choices in life, we determine our individual selves. These doctrines imply that human beings have enormous freedom. Existentialists maintained that the human ability to make free choices is so great that it overwhelms many individuals, who experience a “flight from freedom” by falsely treating religion, science, or other external factors as constraints and limits on individual freedom. In addition to Heidegger the main existentialist thinkers include French feminist philosopher Simone de Beauvoir and her companion, the philosopher, novelist, and playwright Jean-Paul Sartre.

D3 Analytic Philosophy

Analytic philosophy rose to prominence in the United Kingdom after the end of World War I (1914-1918). This movement heralded a linguistic shift according to which the philosophical study of language became the central task of philosophy. Many analytic philosophers concluded that a number of issues prominent in the history of philosophy are unimportant or even meaningless because they arose when philosophers misunderstood or misused language. Analytic philosophy is based upon the assumption that the careful analysis of language and concepts can clear up these problems and confusions. The key figures at the beginning of the movement were British philosopher and mathematician Bertrand Russell and Austrian-born British philosopher Ludwig Wittgenstein.

Russell, strongly influenced by the precision of mathematics, wished to construct a logical language that would reflect the nature of the world. He argued that what he called the “surface grammar” of everyday language masks a true “logical grammar,” knowledge of which is essential for understanding the true meaning of statements. Russell and many philosophers influenced by him asserted that complex statements can be reduced to simple components; if their logic does not permit such reduction, then the statements are meaningless.

Russell’s view was central to the development of the so-called Vienna Circle, a group of analytic philosophers active from about 1920 to 1950, who were led by Rudolf Carnap and Moritz Schlick. The members of the Vienna Circle were scientists or mathematicians as well as philosophers, and they originated the movement known as logical positivism. They believed that the clarification of meaning is the task of philosophy, and that all meaningful statements are either scientifically verifiable statements about the world or else logical tautologies (self-evident propositions). According to the logical positivists the discovery of new facts belongs to science, and metaphysics—the construction of comprehensive truths about reality—is a pretentious pseudo-science.

Wittgenstein, who studied with Russell at Cambridge University, was perhaps the most important analytic philosopher. Like Russell, he distrusted ordinary language. In his Tractatus Logico-Philosophicus (1921) Wittgenstein stated that “philosophy aims at the logical clarification of thoughts.” Philosophy’s function, he believed, is to monitor the use of language by reducing complex statements to their elementary components and by rebuffing all attempts to misuse words in creating the illusion of philosophical depth. “What can be said at all can be said clearly, and what we cannot talk about we must consign to silence.” The Tractatus made important contributions to the philosophy of language, logic, and the philosophy of mathematics. The account of language in Wittgenstein’s later work was much richer and more sophisticated than that in the Tractatus. However, Wittgenstein never abandoned his radical early views on the nature of philosophy.

As the analytic movement developed, different ideas emerged about how philosophical analysis should proceed. A group called constructivists was inspired by Russell, the early writings of Wittgenstein, and the logical positivists. The solutions to philosophical problems, the constructivists argued, lie in using tools of logic to create more precise technical vocabularies. Two leading representatives of this movement were the American philosophers Nelson Goodman and W. V. Quine. Quine saw language and logic as themselves embodying theories about reality, rather than consisting of theory-neutral tools of analysis. By contrast, the descriptivists maintained that philosophical analysis should focus on the careful study of the everyday usage of crucial terms. This group was inspired by the 20th-century British philosophers G. E. Moore, Gilbert Ryle, and John Austin.

Although the radical formulations of analytic philosophy from the first half of the 20th century no longer hold sway, analytic philosophy continues to flourish. Many contemporary philosophers have adopted ideas, methods, or values from the movement, including the Americans Donald Davidson, Hilary Putnam, and Saul Kripke. Analytic philosophy also has widely influenced the training and practices of philosophers today. On the one hand, its influence has led to a renewed commitment to clarity, concision, incisiveness, and depth in philosophical thinking and writing. On the other hand, it has also caused many philosophers to embrace difficult and obscure technical language to such an extent that their ideas are accessible to only a small community of specialists.

D4 Postmodern Philosophy

Inaccessible ideas and impenetrable prose also characterize many postmodern philosophical texts, although the difficulties in this case are often intentional and reflect specific postmodern claims about the nature of language and meaning. The literal meaning of postmodernism is “after modernism,” and in many ways postmodernism constitutes an attack on modernist claims about the existence of truth and value—claims that stem from the European Enlightenment of the 18th century. In disputing past assumptions postmodernists generally display a preoccupation with the inadequacy of language as a mode of communication. Among the major postmodern theorists are French philosophers Jacques Derrida and Michel Foucault, and psychoanalyst Jacques Lacan.

Derrida originated the philosophical method of deconstruction, a system of analysis that assumes a text has no single, fixed meaning, both because of the inadequacy of language to express the author’s original intention and because a reader’s understanding of the text is culturally conditioned—that is, influenced by the culture in which the reader lives. Thus texts have many possible legitimate interpretations brought about by the “play” of language. Derrida stresses the philosophical importance of pun, metaphor, ambiguity, and other playful aspects of language traditionally disregarded in philosophy. His method of deconstruction involves close and careful readings of central texts of Western philosophy that bring to light some of the conflicting forces within the text and that highlight the devices the text uses to claim legitimacy and truth for itself, many of which may lie beyond the intention of its author. Although some of Derrida’s ideas about language resemble views held by the analytic philosophers Wittgenstein, Quine, and Davidson, many philosophers schooled in the analytic tradition have dismissed Derrida’s work as destructive of philosophy.

Foucault created a searing critique of the ideals of the Enlightenment, such as reason and truth. Like Derrida, Foucault used close readings of historical texts to challenge assumptions, demonstrating how ideas about human nature and society, which we assume to be permanent truths, have changed over time. From an array of historical texts Foucault created “philosophical anthropologies” that reveal the evolution of concepts such as reason, madness, responsibility, punishment, and power. By examining the origins of these concepts, he maintained, we see that attitudes and assumptions that today seem natural or even inevitable are historical phenomena dependent upon time and place. He further claimed that the historical development of these ideas demonstrates that seemingly humane and liberal Enlightenment ideals are in reality coercive and destructive.

Lacan agreed with Derrida and Foucault about the need to overturn crucial cultural and philosophical assumptions, but he arrived at this conclusion by a different method altogether. Influenced by Swiss linguist Ferdinand de Saussure and the psychoanalytic theories of Sigmund Freud, Lacan claimed that the unconscious portion of the mind operates with structures and rules analogous to those of a language. He used this claim to criticize both psychoanalytic theory and philosophy. On the one hand, he believed that concepts from linguistics could clarify and correct Freud’s picture of the mind and provide the field of psychoanalysis with greater philosophical depth. On the other hand, he maintained that applying psychoanalytic methods and theories to linguistics would radically revise traditional philosophical views of language and reason.

D5 Feminist Philosophy

Feminist philosophers also challenge basic principles of traditional Western philosophy, investigating how philosophical inquiry would change if women conducted it and if it incorporated women’s experiences as well as their viewpoints. In interpreting the history of Western philosophy, feminists study texts by male philosophers for their depiction of women, masculine values, and biases toward men. Feminist philosophers also write about women’s experiences of subjectivity, their relationship to their bodies, and feminist concepts of language, knowledge, and nature. They explore connections between feminism in philosophy and other emerging feminist disciplines, such as feminist legal theory, feminist theology, and ecological feminism. Central to feminist philosophy is the concept of the oppression of women who live in patriarchal (male-controlled) societies; much of the work of feminist philosophers has gone into understanding patriarchy and developing alternatives to it. Prominent feminist philosophers include French postmodern philosophers Luce Irigaray and Hélène Cixous and American philosopher of law Catharine MacKinnon.

D6 Environmental Philosophy

Environmental philosophy is concerned with issues that arise when human beings interact with the environment. For instance, is a transformation of society necessary for the survival of living organisms and the environment? How is the exploitation of nature related to the subjugation of women and other oppressed humans? How can the philosophical study of the environment guide and inspire effective environmental activism. Most environmental philosophers seek to apply philosophical methods and ideas in collaboration with academics and activists working in the environmental sciences, theology, and feminism.

Two figures who played a prominent role in founding environmental philosophy are Norwegian philosopher Arne Naess and American naturalist, conservationist, and philosopher Aldo Leopold. Naess founded the so-called deep-ecology movement in the 1970s. The movement distinguishes between shallow ecology, which views nature in terms of its value to human beings, and deep ecology, which values nature independently of its usefulness to humanity. Leopold, in his influential book A Sand County Almanac (1949), called for the extension of ethical concern to include all life on Earth, not just human life. Other contemporary environmental philosophers include American ecological theologian Thomas Berry and American ecological feminist Karen Warren.

D7 Contemporary Political Philosophy

Political philosophy dates back to Plato and Aristotle who discussed the nature of the ideal government and the ideal society. It continued in theories on individual liberty and political institutions put forth by Hobbes, Mill, and Rousseau. Political philosophy today features a lively dialogue between defenders of the liberal position and defenders of the communitarian position. The former place the highest value on individual liberties; whereas the latter argue that extreme individual freedom undermines shared community values.

According to liberalism the chief goods (benefits) of government and society are personal and political freedoms, such as freedom of speech, freedom of association, and freedom of conscience (belief). Many liberal theorists view the freedom to make moral choices as the most important freedom; they argue that political and social systems should be organized to allow individuals the freedom to pursue their own ideas about “the good life.” Communitarians respond that granting individuals this extreme freedom of choice ultimately limits human experience by undermining shared communal values. They claim that by ignoring the importance of community, liberalism disregards humanity’s social nature.

Prominent communitarians include Scottish philosopher Alasdair MacIntyre and American philosopher Michael Sandel. Important liberal theorists include British philosopher Isaiah Berlin and American philosophers Ronald Dworkin and John Rawls. Rawls is the author of A Theory of Justice (1971), considered to be the most significant work of political philosophy in the 20th century. In this book, he presents the idea of “justice as fairness,” a principle that promotes the equal distribution of the benefits and burdens of society among individuals. Any advantages that society confers should benefit those who are most disadvantaged, Rawls believes. From this and other principles he has developed theories about political and social relations within liberal democracies and between those democracies and certain illiberal states. Rawls’s ideas remain a major inspiration for much current work in political philosophy.

D8 Applied Ethics

Although most contemporary philosophy is highly technical and inaccessible to nonspecialists, some contemporary philosophers concern themselves with practical questions and strive to influence today’s culture. Practitioners of feminist philosophy, environmental philosophy, and some areas of contemporary political philosophy seek to use the tools of philosophy to resolve current issues directly related to peoples’ lives. Nowhere have philosophers more enthusiastically embraced practical relevance than in contemporary applied ethics, a field that has developed since the 1960s. Most of the questions applied ethicists raise concern the general theme “How should we live and die?”—a question central to ancient Greek philosophy.

Separate areas of specialization, such as biomedical ethics and business ethics, have emerged within applied ethics. Biomedical ethics deals with questions arising from the life sciences and human health care, and has two subspecialties: bioethics and medical ethics. Bioethicists study the ethical implications of advances in genetics and biotechnology, such as genetic testing, genetic privacy, cloning, and new reproductive technologies. For example, they consider the consequences for individuals who learn they have inherited a fatal genetic disease, or the consequences of technology that enables parents to choose the sex of a baby. Bioethicists then offer advice to legislators, researchers, and physicians active in these areas. Specialists in medical ethics offer advice to physicians, other health care personnel, and patients on a wide variety of issues, including abortion, euthanasia, fertility treatments, medical confidentiality, and the allocation of scarce medical resources. Much of the work in medical ethics directly affects the everyday practice of medicine, and most nursing students and medical students now take courses in this field.

Business ethicists bring ethical theories and techniques to bear on moral issues that arise in business. For example, what are the responsibilities of corporations to their employees, their customers, their shareholders, and the environment? Most business students take courses in business ethics, and many large corporations regularly consult with specialists in the field. Business ethicists also address larger topics, such as the ethics of globalization and the moral justification of various economic systems, such as capitalism and socialism.

Reviewed By:
Andrew N. Carpenter

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