Parmenides (c. 510–450 BC)

Greek pre-Socratic philosopher, head of the Eleatic school (so called after Elea in southern Italy). Against Heraclitus's doctrine of Becoming, Parmenides advanced the view that nonexistence was impossible, that everything was permanently in a state of being. Despite evidence of the senses to the contrary, motion and change are illusory – in fact, logically impossible – because their existence would imply a contradiction. Parmenides saw speculation and reason as more important than the evidence of the senses.