Heraclitus

Heraclitus of Ephesus (c. 535–c. 475 BCE) was a pre-socratic philosopher of ancient Greece. He is best known for his obscure writings, his depiction of a universe in flux, and using the term logos philosophically.

Change

Heraclitus believed that change was a fundamental part to the universe. He says “On those stepping into rivers the same, other and other waters flow.” — the famous philosophical idea that one cannot step twice in the same river.

The image of the river, stream or flow is near-constant in Heraclitus' writings. He considers change to be all things to be in a constant state of change, moving back and forth between polar opposites. He considered things to come dually with their opposite, and that the path up and the path down were essentially the same.

Logos

Heraclitus was the first of the Greek philosophers to use the term logos, which means “word”, “account” or “plan”, as a technical one. Heraclitus seems to change back and forth between meanings of the word throughout his work.

Essentially, Heraclitus uses the term logos to describe a fundamental governance of the universe, a sort of universal principle. He says that the Logos is a common thing but that humans fail to notice or understand it.

Heraclitus is described as having been somewhat misanthropic, which is evident both in the pessimistic nature of his writings about the logos, and in discussion from others writing about him. He was sometimes known as “the weeping philosopher”, partly in contrast to Democritus, who was known as “the laughing philosopher”.