Thales (thāˈlēz) [key], c.636–c.546 B.C., pre-Socratic Greek philosopher of Miletus and reputed founder of the Milesian school of philosophy. He is the first recorded Western philosopher. Thales taught that everything in nature is composed of one basic stuff, which he thought to be water. Prior to Thales, mythology had been used to explain the nature of the physical world; the significance of Thales thus lies not in his answer but in his approach. Although he apparently wrote nothing, he is believed to have introduced geometry into Greece and to have been a capable astronomer. It is said he predicted an eclipse of the sun in 585 B.C. Thales studied practical as well as speculative problems and was acknowledged one of the Seven Wise Men of Greece for his exhortation to unity among the Ionian Greeks.
See G. S. Kirk and J. E. Raven, The Presocratic Philosophers (1957).