Thales (ca. 626-ca. 548 BC)

Thales, born in Miletus, was a pre-Socratic Greek philosopher, the first natural philosopher who belonged to the Milesian school along with Anaximander and Anaximenes. Unfortunately, we do not have any of his writings; however, his importance in the field of geographic studies is due particularly to his views about the nature of Earth and his search for rational explanations through the observation of natural phenomena and avoidance of mythological beliefs.

According to Herodotus, Thales predicted the solar eclipse that occurred on May 28, 585 BC, but he is also said to have calculated the length of the seasons, the solstices, and the lunar phases; to have learned from sailors how to orient himself thanks to the stars (especially those belonging to the constellation Ursa Minor); to have conceived of diverting the Halys River (now called the Kizilirmak); and to have studied the yearly floods of the Nile, wrongly believing, however, that they were caused by seasonal winds.

In Egypt, Thales studied geometry and then introduced it to Greece. During his journeys through Egypt, where he visited the Nile delta, Thales observed the areas where water encounters land and elaborated a peculiar cosmological theory based on the idea that water is the origin (arche) of all things and that Earth rests on this substance. According to Aristotle, he may have found support for his idea in the fact that humidity can be found almost everywhere in the world and that moisture provides living beings with nourishment.

Regarding his idea of the shape of Earth, there are two schools of thought: Some commentators argue that he imagined a circular, flat, and thin world, whereas others support the theory that he believed that the planet was spherical. The explanation that he gave of a natural phenomenon such as earthquakes is strictly related to the theory of water as the fundamental principle of the world. In his opinion, in fact, lands fluctuate and shake because of the rough motion of the oceanic sprawl on which they float.