Heraclitus (Stanford Encyclopedia of Philosophy)

Heraclitus, though an Ionian, was not in the scientific tradition of the Milesians.II He was a mystic, but of a peculiar kind. He regarded fire as the fundamental substance; everything, like flame in a fire, is born by the death of something else. “Mortals are immortals, and immortals are mortals, the one living the other’s death and dying the othe

The doctrine that everything is in a state of flux is the most famous of the opinions of Heraclitus, and the one most emphasised by his disciples, as described in Plato’s Theaetetus. “You cannot step twice into the same river; for fresh waters are ever flowing in upon you.”