There is a major watershed figure in ancient Greek philosophy who is so important that events are dated before and after his life. That philosopher is Socrates.

Just as our traditional dating system runs B.C. and A.D., Greek philosophy is divided into the period before Socrates and after. Starting with the Ionians, the earliest philosophers we’re talking about are those before Socrates: the Presocratics.

The Death of Socrates, by Jacques-Louis David (1787)

Bits And Pieces

All we have from the Presocratics are bits and pieces. Imagine picking up teeny scraps of paper after a major tornado destroyed a library. Our fragments from the Presocratics aren’t even that complete. The views of the Presocratics have been reconstructed from isolated quotes found in later works.

Here’s the picture that emerges of the earliest philosophical thought.

Portrait of Socrates. Marble, Roman artwork (1st century), perhaps a copy of a lost bronze statue made by Lysippos.

The Presocratics were materialists. For them, the universe is fundamentally a material universe. With a few qualifications, Greek philosophy begins by exploring various forms of materialism.

The central question for the Presocratics was the ultimate nature of the cosmos. The Ionians were cosmologists: What is the world made of? They wanted a unified answer, a single substance of which everything else is composed.

They’re materialists in that the single thing proposed was almost invariably some material element. Their cosmos was a physical cosmos, composed ultimately of some specific kind of physical stuff. Histories of Western philosophy standardly start with Thales of Miletus, writing around 600 B.C. What is the cosmos made of? Thales’s answer is: water.

This is a transcript from the video series The Great Ideas of Philosophy, 2nd Edition. Watch it now, on The Great Courses Plus.

Everything is One

I’m not a big fan of the 19th-century German philosopher Friedrich Nietzsche, but his reflections on Thales seem absolutely right. Here’s what he says:

Greek philosophy seems to begin with a preposterous fancy, with the proposition that water is the origin and mother-womb of all things. Is it really necessary to stop there and become serious? Yes—says Nietzsche—and for three reasons: Firstly, because the proposition does enunciate something about the origin of things; secondly, because it does so without figure and fable; thirdly and lastly, because in it is contained the idea—Everything is one.

Learn more about how Homer planted the seeds of this reflection



Thales of Miletus c. 624 BC – c. 546 BC

Thales isn’t just spinning a myth about origins; he’s not speaking figuratively. His is a first attempt, a struggling attempt, and perhaps a preposterous fancy, as Nietzsche says. Nevertheless, it’s a first attempt to go beyond myth, to go beyond metaphor or figurative language. It’s a first attempt at a literal theory of the nature of the universe.

A Firmly Materialistic Universe

Thales says that all things in the cosmos are ultimately material, and that ultimate material is water. The Presocratics that follow Thales pick a different substance, but offer a similarly materialistic cosmology. Around 550 B.C., Anaximenes proposes that it’s air that’s the fundamental substance. In Heraclitus, about 500 B.C., it’s fire. Whichever matter is chosen as ultimate, we still have a firmly materialistic universe.

Some of the Presocratics are harder to interpret. Anaximander says that the ultimate material is the indeterminate, but what he seems to have in mind is an indeterminate substance. Around 400 B.C., the atomists—Leucippus and Democritus—come closer to the world that’s reflected in our contemporary science. Leucippus and Democritus envisaged the cosmos as composed of extremely small particles moving randomly in a void, much as we think of atoms.

Learn more about whether or not everything might be reducible to one kind of thing

The Legacy of Greek Philosophy

What’s the legacy of Greek philosophy? A major legacy from the Presocratics is materialism. Most contemporary philosophers, and virtually all contemporary scientific researchers, agree with the Presocratics. The universe is ultimately physical through and through.

Although exploration of materialism occupies center stage in early Greek philosophy, other themes also appear in the Presocratics. Consider the Pythagoreans, a fascinating cross between a religious brotherhood and a research guild.

Pythagoras of Samos; (c. 570 – c. 495) Ionian Greek philosopher and mathematician

The Pythagoreans flourished from the time of Pythagoras himself in the 500s B.C. through intellectual descendants into the 300s. It’s probably from Pythagoras himself that we have the Pythagorean theorem.

A central inspiration of Pythagoreanism seems to have been the fact that the different harmonics of music correspond to mathematical intervals on a stretched string.

What Is The World Made Of?

What’s the world made of? The Pythagorean answer is both an inspiration to contemporary mathematicians and an enigma to everyone else. What is the cosmos made of? The Pythagoreans rejected a cosmos made of water, air, fire, or any other material thing. For them, the cosmos is made of number.

Learn more about Socrates on the examined life

There’s another theme in the Pythagoreans, which also appears elsewhere in Presocratic philosophy. Pythagoras is said to have learned mathematics from the Egyptians. He may have picked up influences from Eastern philosophy there as well.

Part of the Pythagorean corpus was a belief in the transmigration of souls. Where does that fit in a materialistic universe?

Common Questions About Greek Philosophy

This article was updated on 12/20/2019