Heraclitus

Heraclitus was a pre-Socratic philosopher from Ephesus in Ionia, nicknamed in antiquity ho Skoteinos (“the Obscure”) for his riddling style. He is remembered for the doctrine of universal flux — the idea that all things are in constant change — and for his emphasis on the logos and the unity of opposites. His single book, conventionally titled On Nature, survives only in fragments quoted by later writers such as Diogenes Laertius, which is how this saying reaches us.