Heraclitus of Ephesus · c. 500 BC

Nothing is finished.
Everything is becoming.

Heraclitus saw reality as constant change: not being, but becoming. His best-known image is the river. You cannot step into the same river twice, because the water has moved on, and so have you.

Only fragments of his writing survive, and the famous panta rhei, “everything flows”, is a later summary rather than his own words. His opposite was Parmenides, who held that change is an illusion. Their disagreement opened a debate that runs through Western philosophy, from Plato to Hegel and Nietzsche.