Change

Is change real, or an illusion? Heraclitus said everything flows. Parmenides said nothing does. The debate defined metaphysics.

Heraclitus observed that you cannot step into the same river twice. Parmenides countered that true change is logically impossible. This tension (between flux and permanence) drove much of Greek philosophy forward. Plato resolved it by splitting reality into a changing world of appearances and an unchanging world of Forms. Aristotle offered a different resolution through his concepts of potentiality and actuality. The question of what change is remains open.