Lives of Eminent Philosophers (1.prol.21-1.1.25)

One word more: not long ago an Eclectic school was introduced by Potamo of Alexandria,[*], who

It remains to speak of the philosophers themselves, and in the first place of Thales.

Herodotus, Duris, and Democritus are agreed that Thales was the son of Examyas and Cleobulina, and belonged to the Thelidae[*] who are Phoenicians, and among the noblest of the descendants of Cadmus and Agenor. As Plato testifies, he was one of the Seven Sages. He was the first to receive the name of Sage, in the archonship of Damasias[*] at Athens, when the term was applied to all the Seven Sages, as Demetrius of Phalerum mentions in his List of Archons. He was admitted to citizenship at Miletus when he came to that town along with Nileos, who had been expelled from Phoenicia. Most writers, however, represent him as a genuine Milesian and of a distinguished family.

After engaging in politics he became a student of nature. According to some he left nothing in writing; for the Nautical Astronomy[*] attributed to him is said to be by Phocus of Samos. Callimachus knows him as the discoverer of the Ursa Minor; for he says in his Iambics:

Who first of men the course made plain

Of those small stars we call the Wain,

Whereby Phoenicians sail the main.[*].

And some, including Choerilus the poet, declare that he was the first to maintain the immortality of the soul. He was the first to determine the sun’s course from solstice to solstice, and according to some the first to declare the size of the sun to be one seven hundred and twentieth part of the solar circle, and the size of the moon to be the same fraction of the lunar circle. He was the first to give the last day of the month the name of Thirtieth, and the first, some say, to discuss physical problems.

Aristotle[*] and Hippias affirm that, arguing from the magnet and from amber, he attributed a soul or life even to inanimate objects. Pamphila states that,

Others tell this tale of Pythagoras, amongst them Apollodorus the arithmetician. (It was Pythagoras who developed to their furthest extent the discoveries attributed by Callimachus in his Iambics to Euphorbus the Phrygian, I mean scalene triangles and whatever else has to do with theoretical geometry.[*])

Thales is also credited with having given excellent advice on political matters. For instance, when Croesus sent to Miletus offering terms of alliance, he frustrated the plan; and this proved the salvation of the city when Cyrus obtained the victory. Heraclides makes Thales himself[*] say that he had always lived in solitude as a private individual and kept aloof from State affairs.