The great innovation began in the Greek city of Miletus at the beginning of the sixth century B.C. Miletus was a great seafaring power. Her colonies surrounded the shores of the Black Sea and she founded the first Greek settlements in Egypt. There is evidence that the temperament of the Milesians, as of all the Ionian Greeks, was in every way adventurous, exploratory and individualistic.
The very limited information of value which we possess about Thales of Miletus comes to us from a few references in Herodotus and Aristotle. Herodotus tells us that Thales proposed a plan for a federation of the Ionian states with its capital at Teos. A sensible idea like this seems more characteristic of these early thinkers, many of whom were actively engaged in politics, than does the later anecdote of Thales falling into a well because he was so occupied with looking at the stars. Philosophers were not regarded as being odd and unpractical eccentrics until the time of Aristophanes. Herodotus also tells us that Thales successfully predicted an eclipse which was visible in Asia Minor in May, 585 B.C. However, as his successor as leader of thought in Miletus, Anaximander, was certainly ignorant of the true cause of eclipses, we may assume that Thales was also ignorant and was merely applying the rule-of-thumb methods which had long been practiced in Babylonia. So too, though he is said to have been the "father" of geometry, there is in fact no evidence that he was, in the true sense, a mathematician at all. He may well have visited Egypt and have brought back from Egypt to Greece valuable and practical methods of mensuration. That is all.
His importance, then, lies in his teaching, and of this no less an authority than Professor John Burnet writes, "speaking strictly we do not know anything about the teaching of Thales at all." Aristotle indeed attributes to him the sayings that "all things are full of gods" and that "the magnet is alive since it has the power to move iron." But these sayings may easily be later attributions and, even if one accepts them as genuine, they certainly do not provide sufficient evidence to justify us in describing Thales as a pantheist or in forming any theory as regards the particular sort of "life" which was held to animate the magnet.
We are left with the other statement attributed to Thales by Aristotle. This is that the fundamental substance from which all things proceed is water. How he arrived at this doctrine we do not know. A part may well have been played by all sorts of other considerations apart from the obvious ones-the observation of water appearing bath as a liquid, as a solid and as a vapour, the phenomena of rain and of dew, the effect of water on the growth of vegetation, even the old myth that the ocean was the father of all things. What is really important is that the doctrine should have been expressed at all, that a man should have assumed the existence of a coherent universe and should have looked far one underlying reality as a substratum or cause for everything. There is a sense (as was suggested by Lucretius) in which it would be true to say that the distance between Thales and a modern atomic physicist is less great than the distance between Thales and the whole history of civilization before him.