Ionian philosophers

The Ionian school of Pre-Socratic philosophy was centred in Miletus, Ionia in the 6th century BC. Miletus and its environs was a thriving mercantile melting pot of current ideas of the time. The Ionian School included such thinkers as Thales, Anaximander, Anaximenes, Heraclitus, Anaxagoras, and Archelaus. The collective affinity of this group was first acknowledged by Aristotle who called them physiologoi (φυσιολόγοι), meaning 'those who discoursed on nature'. The classification can be traced to the second-century historian of philosophy Sotion. They are sometimes referred to as cosmologists, since they were largely physicalists who tried to explain the nature of matter.

While some of these scholars are included in the Milesian school of philosophy, others are more difficult to categorize.

Most cosmologists thought that, although matter could change from one form to another, all matter had something in common which did not change. They did not agree on what all things had in common, and did not experiment to find out, but used abstract reasoning rather than religion or mythology to explain themselves, thus becoming the first philosophers in the Western tradition.

Later philosophers widened their studies to include other areas of thought. The Eleatic school, for example, also studied epistemology, or how people come to know what exists. But the Ionians were the first group of philosophers that we know of, and so remain historically important.

Thales (Greek: Θαλῆς, Thalēs) of Miletus (c. 624 – c. 546 BCE) is regarded as the earliest Western philosopher. Before him, the Greeks explained the origin and nature of the world through myths of anthropomorphic gods and heroes. Phenomena like lightning and earthquakes were attributed to actions of the gods. By contrast, Thales attempted to find naturalistic explanations of the world, without reference to the supernatural. He explained earthquakes by imagining that the Earth floats on water, and that earthquakes occur when the Earth is rocked by waves. Thales' most famous belief was his cosmological doctrine, which held that the world originated from water.

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