Greek philosophy began not in Athens but on the edges of the Greek world, in the trading cities of Ionia (the west coast of modern Turkey) and in the Greek colonies of southern Italy. The thinkers who worked there in the sixth and fifth centuries BCE are called the Presocratics, a modern label meaning simply that they came before Socrates or were his contemporaries. Most of their books are lost. We know them through fragments, short quotations preserved by later writers, and through reports by authors such as Aristotle.

The turn from myth

Earlier Greeks explained the world through stories about gods. Hesiod's poem the Theogony tells how the cosmos came from Chaos and how gods were born, fought and ruled. The Presocratics did something new. They looked for natural explanations that anyone could examine and argue against, and they asked what basic stuff or principle (the Greek word is arche) lies behind all change. This shift is often called the move from mythos to logos, from story to reasoned account. It was not a clean break, since several Presocratics still spoke of the divine, but the method changed: claims now came with reasons.

The Milesians

Thales of Miletus is traditionally counted the first philosopher. Ancient writers say he predicted a solar eclipse, usually dated to 585 BCE, and Aristotle reports that he held water to be the origin of all things. His successor Anaximander proposed instead a boundless, indefinite stuff (the apeiron), and Anaximenes proposed air, which thickens into water and earth and thins into fire. The answers were wrong, but the questions were bold, and each thinker criticized the one before. That habit of criticism is perhaps their greatest gift.

Heraclitus and Parmenides

Heraclitus of Ephesus (active around 500 BCE) taught that the world is in constant change, held together by a hidden order he called the logos. He favored fire as the image of reality and loved paradox: opposites such as day and night, or war and peace, depend on each other. Plato reports his most famous idea in the form “you cannot go into the same water twice,” because new waters are always flowing on.

Parmenides of Elea, in southern Italy, argued the opposite in a philosophical poem. Starting from the claim that what is not cannot be thought or spoken of, he concluded that real being must be one, unchanging and eternal, and that the change our senses report is illusion. His student Zeno defended him with paradoxes, such as the claim that swift Achilles can never overtake a tortoise with a head start, since he must always first reach the point the tortoise has just left.

The atomists

Later thinkers tried to rescue change from Parmenides. Empedocles proposed four elements (earth, water, air and fire) mixed by Love and separated by Strife. Leucippus and his follower Democritus of Abdera proposed that reality consists of tiny, indivisible particles moving in empty space. The Greek atomos means “uncuttable.” Atoms themselves never change, which honors Parmenides, but their rearrangement explains the changing world we see. Democritus even suggested that colors and tastes exist “by convention,” while in truth there are only atoms and the void.

Ancient atomism was not modern science: it rested on reasoning, not experiment. Yet it shows the Presocratic spirit at its best. Faced with a hard argument, they did not appeal to tradition. They built a better theory. Two other figures deserve a mention: Pythagoras and his followers, who saw number as the key to the cosmos, and Xenophanes, who mocked the idea that gods look like humans, noting that if oxen could draw, they would draw gods like oxen.

Worked example: explaining an earthquake

Imagine a Greek town in the sixth century BCE shaken by an earthquake. How might different people explain it?

A traditional answer comes from myth: Poseidon, god of the sea and “earth-shaker,” is angry. The explanation is complete in its own way. It tells you who caused the event and what to do (offer sacrifice). But it cannot be tested. If the next sacrifice is followed by another quake, the priest can say the god was still angry.

Now picture a Milesian thinker. Ancient reports say Thales suggested that the earth floats on water, so quakes happen when the water moves. Anaximenes is said to have blamed the earth cracking as it dries out and soaks up rain. Both answers are wrong. But notice what they share:

• They point to a natural cause that works the same way every time.
• They can be compared and criticized: if the earth floats on water, what does the water rest on? Aristotle later asked exactly that.
• They invite a better theory rather than a bigger sacrifice.

Try one more step. A follower of Parmenides would ask whether anything really changes at all, since the senses may deceive us. An atomist would answer that atoms never change but can shift and collide, so a quake is atoms in motion. Each step does not simply add a new opinion. It answers a problem the last thinker left open. That chain of argument and objection is what “the turn from myth to reason” means in practice.