Nothing Thales (c. 624–546 BCE) wrote survives; we know him through later witnesses — Aristotle, Herodotus, Diogenes Laertius. Yet antiquity placed him at the head of the Seven Sages, and Aristotle's *Metaphysics* names him as the starting point of philosophy itself.

The central question was simple: *what is everything*? Thales's answer was equally simple and radical: the *arche*, the underlying first principle, is water. What mattered was not the choice of water but the move itself — the search for a natural, material principle behind appearances, rather than appealing to the Olympian gods. Lightning was no longer the wrath of Zeus but a phenomenon awaiting explanation.

Herodotus reports that Thales predicted the solar eclipse of 28 May 585 BCE, which was striking enough to halt a battle between the Lydians and the Medes. Whether the prediction rested on Babylonian astronomical tables or was a lucky inference remains debated — but the story itself records a new idea: that nature can be foreknown through observation and number.

Thales's Milesian successors, Anaximander and Anaximenes, proposed rival principles — the boundless *apeiron*, air — but the question was his. Most histories of science and of philosophy therefore begin at the same address: 'around 585 BCE, in Miletus.'