body of philosophical concepts developed by the Greeks, particularly during the
flowering of Greek civilization between 600 and 200BC. Greek philosophy formed
the basis of all later philosophical speculation in the Western world. The
intuitive hypotheses of the ancient Greeks foreshadowed many theories of modern
science, and many of the moral ideas of pagan Greek philosophers have been
incorporated into Christian moral doctrine. The political ideas set forth by
Greek thinkers influenced political leaders as different as the framers of the
U.S. Constitution and the founders of various 20th-century totalitarian states.
Greek philosophy may be
divided between those philosophers who sought an explanation of the world in
physical terms and those who stressed the importance of nonmaterial forms or
ideas. The first important school of Greek philosophy, the Ionian or Milesian,
was largely materialistic. Founded by Thales of Miletus in the 6th century BC,
it began with Thales' belief that water is the basic substance out of which all
matter is created. A more elaborate view was offered by Anaximander, who held
that the raw material of all matter is an eternal substance that changes into
the commonly experienced forms of matter. These forms in turn change and merge
into one another according to the rule of justice, that is, balance and
proportion. Heraclitus taught that fire is the primordial source of matter, but
he believed that the entire world is in a constant state of change or flux and
that most objects and substances are produced by a union of opposite principles.
He regarded the soul, for example, as a mixture of fire and water. The concept
of nous ("mind"), an infinite and unchanging substance that
enters into and controls every living object, was developed by Anaxagoras, who
also believed that matter consisted of infinitesimally small particles, or
atoms. He epitomized the philosophy of the Ionian school by suggesting a
nonphysical governing principle and a materialistic basis of existence.
THE ELEATIC SCHOOL, AND THE SOPHISTS
The division between idealism
and materialism became more distinct. Pythagoras stressed the importance of form
rather than matter in explaining material structure. The Pythagorean school also
laid great stress on the importance of the soul, regarding the body only as the
soul's "tomb." According to Parmenides, the leader of the Eleatic
school, the appearance of movement and the existence of separate objects in the
world are mere illusions; they only seem to exist. The beliefs of Pythagoras and
Parmenides formed the basis of the idealism that was to characterize later Greek
A more materialistic
interpretation was made by Empedocles, who accepted the belief that reality is
eternal but declared that it is composed of chance combinations of the four
primal substances: fire, air, earth, and water. Such materialistic explanations
reached their climax in the doctrines of Democritus, who believed that the
various forms of matter are caused by differences in the shape, size, position,
and arrangement of component atoms. Materialism applied to daily life inspired
the philosophy of a group known as the Sophists, who were active in the 5th
century BC. With their stress on the importance of human perception, such
Sophists as Protagoras doubted that humanity would ever be able to reach
objective truth through reason and taught that material success rather than
truth should be the purpose of life.
In contrast were the ideas of
Socrates, with whom Greek philosophy attained its highest level. His avowed
purpose was "to fulfill the philosopher's mission of searching into myself
and other men." After a proposition had been stated, the philosopher asked
a series of questions designed to test and refine the proposition by examining
its consequences and discovering whether it was consistent with the known facts.
Socrates described the soul not in terms of mysticism but as "that in
virtue of which we are called wise or foolish, good or bad." In other
words, Socrates considered the soul a combination of an individual's
intelligence and character.
The idealism of Socrates was
organized by Plato into a systematic philosophy. In his theory of Ideas, Plato
regarded the objects of the real world as being merely shadows of eternal Forms
or Ideas. Only these changeless, eternal Forms can be the object of true
knowledge; the perception of their shadows, that is, the real world as heard,
seen, and felt, is merely opinion. The goal of the philosopher, he said, is to
know the eternal Forms and to instruct others in that knowledge.
Plato's theory of knowledge is
implicit in his theory of Ideas. He argued that both the material objects
perceived and the individual perceiving them are constantly changing; but, since
knowledge must be concerned only with unchangeable and universal objects,
knowledge and perception are fundamentally different.
In place of Plato's doctrine
of Ideas with a separate and eternal existence of their own, Aristotle proposed
a group of universals that represent the common properties of any group of real
objects. The universals, unlike Plato's Ideas, have no existence outside of the
objects they represent. Closer to Plato's thought was Aristotle's definition of form
as a distinguishing property of objects, but with an independent existence apart
from the objects in which it is found. Describing the material universe,
Aristotle stated it consists of the four elements, fire, air, earth, and water,
plus a fifth element that exists everywhere and is the sole constituent of the
heavenly bodies "above" the moon.
In the writings of Plato and Aristotle the dominant strains of
idealism and materialism in Greek philosophy reached, respectively, their
highest expression, producing a body of thought that continues to influence
philosophical inquiry. Subsequent Greek philosophy, reflecting a historical
period of civil unrest and individual insecurity, was less concerned with the
nature of the world than with the problems in the individual. During this period
four major schools of largely materialistic, individualistic philosophy arose:
that of the Cynics, and those espousing Epicureanism, Skepticism, and Stoicism.
For a detailed history of these and earlier schools, see Philosophy. For
additional information on individual philosophers, see biographies of those
whose names are not followed by dates.