Heraclitus

Heraclitus of Ephesus was a pre-Socratic philosopher known for his cryptic, aphoristic style and his central doctrine that everything is in constant flux. He believed fire was the fundamental element of reality and that change itself was the one constant principle governing the cosmos.

His concept of the Logos — a rational principle underlying the apparent chaos of change — anticipates later ideas in Stoicism and Christian theology. For Heraclitus, most people sleepwalk through a world whose rational structure they never perceive.