Pre-Socratic philosophy is a term for the theories developed by Greek philosophers from about 600 B.C. to 400 B.C. These philosophers are called pre-Socratic because most of them preceded Socrates, the famous philosopher of Athens. The pre-Socratics tried to understand and explain the natural universe in terms of natural principles. They developed conflicting theories but shared a basic interest in the origin and natural processes of the universe. The pre-Socratics laid the foundation for the work of later philosophers.
Scholars know little about the pre-Socratics. Their knowledge comes mainly from fragments of pre-Socratic writings and the works of later writers.
The first pre-Socratics
lived in Miletus, a Greek city in Asia Minor, during the 500’s B.C. These philosophers believed the universe originated from, and is composed of, one basic substance. The first known pre-Socratic, Thales, taught that water was this substance. Another member of the group, Anaximander, thought the universe came from an eternal stuff that he called the indefinite. Anaximenes theorized that air was the basic substance and that it condensed or became less dense to form other materials, such as water or fire.
At about the same time, in what is now southern Italy, Pythagoras explained the universe in terms of numbers. He taught that all things are numbers or, perhaps, could be reduced to numbers. Pythagoras also believed that everything is harmoniously related. On the other hand, Heraclitus saw only strife in the world. He thought that everything constantly changes and moves, and that nothing remains the same.
The teachings of Parmenides,
which became influential during the 400’s B.C., raised a problem for other pre-Socratics. Until then, philosophers had accepted the existence of change, motion, and plurality (reality consisting of many substances). Parmenides held that change, motion, and plurality were unreal because they require the existence of what is not. Parmenides rejected the idea of what is not as inconceivable. He said the universe is uniform, immovable, and unchanging, with no generation or destruction.
Parmenides had few followers but great influence. His opponents could not disprove his reasoning, and so they tried to reconcile his conclusions with common sense. Empedocles agreed that there could be no generation or destruction. He explained their apparent existence in terms of four eternal elements–earth, air, fire, and water–mixed by the force of love and separated by strife. Anaxagoras believed an infinite number of elements had been separated out of an original mixture through the rotation initiated by a force or material he called Mind. Each kind of natural substance contains all the elements but in different proportions. Anaxagoras thought matter was infinitely divisible.
In the late 400’s B.C., Leucippus and Democritus responded to Parmenides with a theory called atomism. They taught that the universe consists of tiny, solid, indivisible bodies called atoms, which move about in space and cluster together to form the larger objects of common experience.
