It is with Thales that physics, geometry, astronomy, and philosophy have long been thought to begin. However, little is known of the first supposed identifiable ‘scientist’ apart from the fact that he was born at Miletus, now in Turkey, and a number of anecdotes that clearly originate in folklore.

Thus he is traditionally supposed to have acquired his learning from Egypt, an implausible claim when the modest mathematical skills of sixth-century Egypt are contrasted with the supposed achievements of Thales. To him is even attributed a proof of the proposition that the circle is divided into two equal parts by its diameter, a theorem not to be found in Euclid some 300 years later. It is also reported by the historian Herodotus that Thales gave a prediction of a solar eclipse in 585 bc.

The remaining claim for Thales rests on his introduction of naturalistic explanations of physical phenomena in opposition to the customary understanding of nature in terms of the behavior of the gods. Hence the importance of his claim that everything is water, perhaps the first recorded general physical principle in history.