Ancient Greek and Roman · c. 500 BCE
The Presocratics
Overview
The first Greek arguments about nature: all things change, nothing comes from nothing, and change has to be explained.
The Presocratics are the Greek thinkers before Socrates, from the sixth and fifth centuries BCE. Their books are lost, and they survive in fragments quoted by later writers. They asked what the world is made of and how it changes, and they answered with arguments rather than stories about the gods. That shift is often taken as the start of Western philosophy.
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Heraclitus of Ephesus saw the world as a steady pattern of change. A river stays a river because new waters keep flowing, and opposites such as up and down or sickness and health belong together. Behind the flux he placed a logos, an account common to everyone. Parmenides of Elea argued the reverse: what is not cannot be, so nothing comes into being or changes, and the changing world is opinion. His follower Zeno defended him with paradoxes of motion.
Later thinkers spent generations answering Parmenides. The atomists, Leucippus and Democritus, kept his rule that nothing comes from nothing and explained change as atoms moving in the void. Plato tried to join a stable world of Forms to a changing world of things. The habit worth keeping is to ask what flows under the things that seem fixed, and to test an argument whose conclusion you cannot believe.
Where it answers
What is real?
Look for the one stuff or law beneath all change: water, fire or unchanging being.
Key terms
- Flux
- Heraclitus’s view that everything is always changing, like a river.
- Logos
- For Heraclitus, the rational order behind constant change.
- Unity of opposites
- Heraclitus’s claim that opposites, such as day and night, belong together.
- What is
- Parmenides’s argument that being is one and unchanging, so change is an illusion.
- Way of opinion
- Parmenides’s name for the misleading world the senses show.
Further reading
- Heraclitus, fragments
- Parmenides, On Nature
- Zeno, paradoxes
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Quest2Reason. “The Presocratics.” https://quest2reason.com/learn/ideas/presocratics. Accessed 13 November 2026.