About 600 B.C., the Greek cities of Ionia were the intellectual and cultural leaders of Greece and the number one sea-traders of the Mediterranean. Miletus, the southernmost Ionian city, was the wealthiest of Greek cities and the main focus of the "Ionian awakening," a name for the initial phase of classical Greek civilization, coincidental with the birth of Greek philosophy.
The first group of Greek philosophers is a triad of Milesian thinkers: Thales, Anaximander, and Anaximenes. Their main concern was to come up with a cosmological theory purely based on natural phenomena. Their approach required the rejection of all traditional explanations based on religious authority, dogma, myth and superstition. They all agreed on the notion that all things come from a single "primal substance": Thales believed it was water; Anaximander said it was a substance different from all other known substances, "infinite, eternal and ageless"; and Anaximenes claimed it was air.
Observation was important among the Milesian school. Thales predicted an eclipse which took place in 585 B.C. and it seems he had been able to calculate the distance of a ship at sea from observations taken at two points.

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