The Eclipse That Anchors an Uncertain Life

Almost nothing about Thales rests on a document written in his own lifetime, since no writing by him survives and no contemporary source confirms the stories later Greeks told about him. One detail, however, gives historians unusually solid footing: ancient accounts, including Herodotus, report that Thales predicted a solar eclipse that interrupted a battle between the Lydians and the Medes, and modern astronomical calculation identifies a total eclipse visible from Asia Minor on May 28, 585 BCE, an event that lets historians anchor the otherwise vague dates of his life to one real day in the sky. What made Thales matter to later philosophy was not prediction but a different kind of claim: that beneath the changing variety of things in the world lies a single underlying substance, which he identified as water, the arche or first principle from which everything else somehow arises or into which it somehow resolves. That was a genuinely new kind of question, an attempt to explain nature through nature's own materials rather than through the actions of gods, and Aristotle treats Thales as the point where Greek philosophy properly begins for exactly that reason. Later Milesian thinkers, Anaximander and Anaximenes, kept Thales's question but rejected his answer, proposing the boundless and air respectively as the true first principle, evidence that a school had formed around a shared problem rather than a fixed doctrine.