Pre-Socratic Philosophy

The pre-Socratics were Greek philosophers who speculated about the nature of the world for more than 150 years before Socrates flourished. Their philosophizing about nature sought answers to questions that were metaphysical and scientific, although these disciples were not then separated. The metaphysical questions asked by the pre-Socratics were inquiries into the ultimate nature of everything.

Their questions included What is the beginning (arche) or source of all things? What is reality and what is only appearance? What is everything made of? Is it one "stuff" or many "stuffs?" This last question is now called the problem of "the one and the many". Other problems addressed by the pre-Socratics included the nature of change, of being, of becoming, and quantity.

The great importance of the pre-Socratics lies in their speculative use of reason without reference to myths, authorities, religion, popular opinion, or other sources of knowledge. They used reason to supply answers about the metaphysical nature of the universe.

In doing so they initiated a great philosophical conversation that applies human reason to the quest to understand everything. The pre-Socratics were a varied group of thinkers, but all were Greeks. They lived and worked in widely scattered locations. Most of their writings were lost in antiquity.

Fragments, along with testimonia (what was reported by other writers as direct quotations or as summaries of their thought), have survived that give a general picture of their thought. The fi rst school of the pre-Socratics was the Ionian school. These Ionian Greeks produced the Milesian school and two independent philosophers.

Milesian School

The first Greek philosopher, according to Aristotle, was Thales (c. 624–545 b.c.e.). He was counted as one of the legendary Seven Sages and the founder of the Milesian school. His polis (city-state), Miletus, was located on the southwestern coast of what is now Turkey.

Thales is noted for predicting an eclipse of the Sun in 585 b.c.e. More important, he explained why the eclipse would occur, saying that it would occur when the Moon passed between the Sun and the Earth. The Moon would consequently block the rays of the Sun and would cast its shadow on the Earth until it moved on in its orbit around the Earth.

This explanation was a naturalistic explanation. It did not rely on the religious mythopoeic explanations of gods, demons, or other spiritual forces that abounded in the beliefs of that time. This explanation is counted as the beginning of Western philosophy. It served as a corrective to the poetic views of Homer, Hesiod, and other Greek poets.

Thales, in a search for the ultimate unity of the cosmos, pondered the question What is everything made of? His answer was water. This seemed to be a plausible answer because much of the surface of the Earth is covered with water; water comes in solid, liquid, and gaseous states, and water is the basis of life on Earth.

However, the answer, while wrong, is valuable because it can be "falsified". Answers to questions that can neither be proven as true or false have little value. Those that can be falsified shut the door to further research in that area and direct inquiry to other areas.

Thales’s immediate follower was Anaximander (c. 610–545 b.c.e.), the second member of the Milesian school. Anaximander speculated that the basic "stuff" of the cosmos was not water. Instead, he reasoned it was an odorless, colorless, weightless substance that he called "the boundless" (aperion).

His thought was that aperion was the arche, or source of all things, and it was infinite in supply. His answer also initiated "philosophical criticism" because it was a reasoned analysis of the speculations of Thales.

For Anaximander all particular things such as earth, air, fire, and water had been spun out of the whirling mass of the boundless. These particulars were in constant warfare with each other. This viewpoint presented a primitive form of the idea of evolution.

However, his view of "evolution" was cyclical. He argued that the continual change in the cosmos was part of a cycle of creation and destruction. By adding time to his speculative ideas he was able to express a cyclical view of history. In addition, by using reasoning about the unseen ultimate nature of the cosmos he introduced a primitive rationalist method.

Anaximenes (c. 560–28 b.c.e.) was the third member of the Milesian school. He was a younger contemporary of Anaximander. He rejected the speculation of Anaximander that aperion is the basic stuff of the universe. He reasoned that the answer is of limited use because there is too little that can be known about a stuff that is "unbounded".

Agreeing with Anaximander that the basic stuff should be eternal, unlimited, and at the same time a singular "stuff", and using the criterion of clarity, Anaximenes declared that all thing are derived from air. When this assertion is compared to the gaseous state of the universe immediately after the "big bang", when all matter everywhere was stripped to protons, his answer can be viewed as surprisingly modern.

Independent Ionian Philosophers

The first of the independent Ionian philosophers was Heraclitus of Ephesus (fl. c. 500 b.c.e.). He is known as the philosopher of flux because he asserted that everything is changing and that the only thing that does not change is change itself. He is famous for the saying "I can step into a river once, but I cannot step into the same river twice".

This means that the basic characteristic of the cosmos is "becoming". Everything is constantly becoming something else. Heraclitus taught that the basic "stuff" is fire. He went beyond physical fire to argue that the fire was a divine reason, or logos, that was constantly in motion. He used the metaphor of law courts to include a moral vision to his philosophy.

The cosmos is constantly changing, but there is a pattern such that "justice" (dike) seeks to establish a balance. Constantly, if there is an "offense" it must be balanced. This vision of the world was to greatly influence adam smith’s vision of the "harmony" (harmonia or concordia) of the marketplace that is controlled by an "invisible hand".

Xenophanes (c. 560–470 b.c.e.) of Colophon (located 40 miles north of Miletus) is included among the Ionians, but Aristotle placed him among the Eleatics. He lived for a time in Sicily and at Elea, where he may have founded Eleatic philosophy.

Xenophanes’ contribution to philosophy was a radical critique of popular Greek religion, specifically the works of Homer (Iliad and Odyssey) and Hesiod (Theogony). The Greeks were polytheists with the Olympian gods serving as the public state gods. For Xenophanes the Olympian gods lacked moral inspiration and were shameful.

His critique began the philosophy of religion. Xenophanes was neither an atheist nor an agnostic but believed in one god that was greater than any other and who was utterly different. He also accepted the common ancient belief that order was the sign of intelligence that ultimately was divine.

All of the Ionian pre-Socratic philosophers were materialistic monists. As metaphysical monists their claim was that the basic "stuff" of the cosmos was a single material substance (monism).


Pythagoras (c. 570–495 b.c.e.) was a monist, but in contrast to the materialism of the Ionians, he was an idealist (or immaterialist). Pythagoras is classified as a member of the Italian school of pre-Socratic philosophers. According to legend, one day Pythagoras walked by the blacksmith’s shop and heard the tones of different hammers beating on the anvil.

He went home and worked with notes produced by different lengths of string. From his experiments he concluded that the basic stuff of the universe is numbers. It was in effect a discovery of quantity—every physical thing in the cosmos has quantity associated with it.

Pythagoras organized a school that was more of a mathematical cult, open to both men and women. The Pythagorean school flourished, and eventually the Pythagoreans took control of several city-states. The greatest success of Pythagoras in mathematics was the Pythagorean formula (A2 + B2 = C2). The formula says that the sum of the squares of the lengths of the sides of a right-angled triangle is equal to the square of its hypotenuse.

All went well until it was discovered that if sides A and B of a triangle were equal in length, then the resulting square root would be an "irrational" number. When news of hypotenuses with irrational numbers leaked out of the inner circle of Pythagoreans, it meant that the Pythagorean belief that everything could be rationally comprehended by mathematics was flawed.

The natives rose up in revolt and attacked the Pythagoreans. In the violent turmoil Pythagoras fled for his life, but coming upon a bean field he stopped and would not cross it because he believed that beans were sinful. He was soon caught and killed, but the teachings of the Pythagorean school lived on.

Eleatic School

The city-state of Elea, south of Naples on the western Italian peninsula, was the home of the Eleatic school of pre-Socratics. The first of these was Parmenides, whose method was rationalistic. He challenged the claim of Heraclitus that everything was in flux.

For Parmenides (515–c. 450 b.c.e.) the basic "stuff" of the cosmos is being. Everything that exists "is". It has the property of "is-ness" because it "exists". This is in contrast to not being or "no-thingness" (nothingness). For Parmenides change was an illusion.

If a thing exists then it "is", and if it "is", then it cannot both be and not be at the same time by somehow being and then changing to become something else. Parmenides’ argument is a radical affirmation of being. As a rationalist, Parmenides argued for "the Way of Truth" and rejected "the Way of Opinion".

The second of the Eleatics was Zeno of Elea (c. 470 b.c.e.). He is famous for paradoxes he posed to demonstrate that change is an illusion. Some of his paradoxes are about the experience of motion. They seek to demonstrate that belief in motion entraps those who believe in motion as a form of change into an impossible contradiction.

His paradoxes included "The Stadium", "The Runner", "The Race between Achilles and the Tortoise" and "The Arrow". The goal of each paradox was to lead opponents into a reductio ád absurdum in which motion was seen as a confused condition of life.

The Pluralists are those pre-Socratic philosophers who claimed that the basic stuff of the cosmos were many. This school includes two independent thinkers, most notably Empedocles and Anaxagoras. Empedocles (c. 495–435 b.c.e.) flourished in Sicily. Ancient legend says that he ended his life by jumping into the crater of Mount Etna.

For Empedocles the basic "stuff" of the universe is plural. Specifically everything is made of earth, air, fire, and water. Aristotle agreed with his views and spread them widely. "On Nature" and "Purifications" are two poems by Empedocles and are the longest surviving works of the pre-Socratics.

The thought of Parmenides influenced Empedocles in several ways. For both men reality was a complete plenum. There is, in their view, a plenitude of being in the cosmos so that there are no gaps where there is "nothing". They also agreed that nothing comes into existence nor goes out of existence. Nor do things move in empty space.

Empedocles is reported by the ancients as having found fossils in the high mountains of Sicily. He concluded that life began in the sea. His poem "On Nature" presents a proto-evolutionary view of the development of the world in which the four elements of the universe—earth, air, fire, and water—are combined and destroyed by the forces of love and strife.

For Empedocles random combinations create the world cycle. However, he also believed that there was a god of the process. He held it to be a flashing sacred mind that influenced the cosmos with rapid thought of its divine mind.

Anaxagoras (c. 500–428 b.c.e.) was from Clazomenae in Asia Minor. He taught in Athens and for a short time taught Socrates. Questionable sources say that he was convicted of teaching impiety by declaring that the Sun was a red-hot rock.

Unlike Socrates, who would be executed some year later on a similar charge of impiety, Anaxagoras was exiled from Athens because of the intervention of Pericles, his former student. Anaxagoras reworked the thought of Empedocles. He rejected the idea that the four basic elements are earth, air, fire, and water, which combine and disintegrate due to the forces of love and strife.

Instead, he asserted that there was an infinite variety of minute "seeds" that are the basis for all of the variety of things in the world. Moreover, many new combinations of the seeds create the myriad objects in the world because of the actions of an orderly divine mind, or nous in Greek.


The final school of Pluralists was the Atomists: Leucippus (c. fifth century b.c.e.) of Elea or Miletus, and Democritus (c. 460–370 b.c.e.) of Abdera. Little is known of Leucippus, who may have studied with Zeno. It is believed that Democritus studied with Leucippus, and scholars believe that their teachings were essentially the same.

Democritus taught that if he took a rock or some material and crushed it until it was no longer cut-able, then he would have "a-tome". The Greek word tome means "to cut", and the prefix a- means "un-". The result of the cutting of a thing to its uncut-able state would be an atomos, or in the plural, atomoi. Modern atoms are taken from this ancient idea but are qualitatively different.

Democritus was a pluralist. For him there were in the cosmos a myriad of different atomoi. Some were small and smooth like small ball bearings, others were sticky like Velcro, while others were rough with hooks, or others very tiny and dissipated quickly like perfume.

For Democritus even the gods were made of atoms moving in the vortex of the cosmos, which appeared to the ancients as the Milky Way. Two implications of this materialist pluralism were a denial of the eternity of the gods and the denial of punishment in an afterlife. For Democritus material things in the cosmos had been created by the myriad atomoi combining as they moved in the vortex.

The "furniture" of the cosmos (which for the Greeks included everything that is) was the result of accidental "makings" caused by the bumping together and the separation of the myriad different atomoi, which produced and by separating destroyed the world.

Furthermore, the atomoi moved in empty space that was not "nothing" as Parmenides had taught, but a "no-thing" in empty space. In this way Democritus distinguished between a void in which there are no material bodies and nothingness, which is the total absence of space and any body as well. The implications were that souls were atoms that quickly dissipated and that the gods would go in their turn as well.

Hence, there would be no eternal survival of the soul and no judgment in a life to come. At the end of the era of the pre-Socratics no solution had been found that was a conclusive analysis of the nature of the cosmos. Their work would be utilized by both Plato and Aristotle in their struggles against the Sophists.