An idea · Pre-Socratic · first attested 600 BCE
The Arche (the underlying stuff)
What is the one substance behind the many things we see?
The first philosophical question, asked around 600 BCE in Miletus: what is the arche — the underlying stuff, principle, or origin from which everything else comes? Thales said water; Anaximenes said air; Anaximander said an indefinite, boundless something. The answers vary; the question is the revolutionary part. Asking it presupposes that the world is one thing in disguise, that reason can find the disguise, and that gods need not be the explanation.