Thales of Miletus

Thales is the first person in the Western tradition who tried to explain the world without invoking the gods. Living in the Greek port-city of Miletus around 600 BCE, he asked a question so simple it had never been asked before: what is everything made of? His answer — water — sounds quaint, but the move was revolutionary. He replaced myth with a hypothesis, and a hypothesis is the first form of science and the first form of philosophy.

Almost nothing of his writing survives. We know him through later philosophers who treated him as the patriarch. Aristotle credits him as the first to look for an underlying substance (an arche) of the cosmos.

Thales is the inaugural gesture of Western philosophy: the willingness to suppose that the world is intelligible, and that a person can figure it out by thinking.