Philosopher

Heraclitus

fl. 510–490 BCE

Also known as Heraclitus of Ephesus

Ephesian thinker who held that everything is in flux, that opposites form a unity, and that change is governed by a rational principle, the logos.

Painting of a bearded, melancholy man resting his head on his hand — Abraham Janssens, about 1601, an imagined portrait of Heraclitus as the "weeping philosopher".Abraham Janssens · Public domain · See the original

You cannot go into the same water twice.

As reported by Plato, Cratylus 402a, translated by Benjamin Jowett

Heraclitus wrote in short, riddling sayings, of which only fragments survive, quoted by later authors. He is best known for the idea that things are constantly changing, later summed up in the saying that you cannot step into the same river twice, and for the claim that opposites such as day and night, or war and peace, belong together as a unity. He took fire to be the basic stuff of the world, and spoke of a logos, an underlying account or law, that governs all change.

Ancient readers found him deliberately difficult and nicknamed him “the Obscure”. His dates are approximate: he was active around 500 BCE.

Key ideas

Everything flows: “On those stepping into rivers staying the same, other and other waters flow.” Plato summed up Heraclitus as saying that all things pass and nothing stays, so you can’t step twice into the same river.
The unity of opposites: “Sea is the purest and most polluted water: for fish drinkable and healthy, for men undrinkable and harmful.” Opposites such as waking and sleeping are found in the same thing, as each changes into the other.
Fire and transformation: Heraclitus is best known for making fire the basic material of the world. He also describes elements being born from one another’s deaths (“for souls it is death to become water”).
The logos: “Having harkened not to me but to the Word (Logos) it is wise to agree that all things are one.” Wisdom needs a better grasp of the message the world offers, not just more information, and his riddling sayings make readers work for it.

Tradition: Western
Region: Ephesus, Ionia
Period: Ancient Greek and Roman

Influences

Heraclitusfl. 510–490 BCE

Influenced

Heraclitusfl. 510–490 BCE

Influenced

Where these links come from

Plato drew on Heraclitus. Source: Daniel W. Graham, Heraclitus, Stanford Encyclopedia of Philosophy
Marcus Aurelius drew on Heraclitus. Source: Rachana Kamtekar, Marcus Aurelius, Stanford Encyclopedia of Philosophy

Sources

Daniel W. Graham, Heraclitus, Stanford Encyclopedia of Philosophy