Thales (650 BCE - 548 BCE) was an ancient Greek philosopher, mathematician and astronomer from Miletus in Ionia, on the coast of Asia Minor. [1] He is traditionally regarded as the first philosopher in the Western tradition, because he sought to explain natural events through natural causes rather than divine agency. Later writers credited him with geometric theorems, an early cosmology based on water, and the prediction of a solar eclipse. [2]
Life and sources
Almost nothing about Thales can be established with certainty. He lived in Miletus, then the wealthiest Greek city of Ionia, during the late seventh and early sixth centuries BCE; the dates conventionally assigned to him are approximate and derive from much later chronographers. [1] No writing by Thales survives, and everything attributed to him comes through later authors, above all Aristotle and the third-century CE compiler Diogenes Laertius. [3]
Ancient tradition lists him among the Seven Sages of Greece, a group of early figures honoured for practical and political wisdom. Stories place him in Egypt, where he was said to have learned geometry, and credit him with advising Ionian cities on political federation and with engineering feats such as diverting a river for an army crossing. [2]
Natural philosophy
Aristotle presents Thales as the founder of the enquiry into nature, on the grounds that he asked what single material principle underlies all things and answered that it is water. Thales reportedly held that the earth floats on water, and that all things are in some sense full of gods or alive, a view later writers connected with his explanation of magnetism. [3]
This shift from mythological narrative to reasoned natural explanation is why Thales is placed at the head of the Milesian school, which continued with Anaximander and Anaximenes, and at the beginning of Greek philosophy and science. [1]
Mathematics and astronomy
Thales is credited by later Greek sources with introducing deductive geometry to Greece and with several elementary results, including the propositions that a circle is bisected by its diameter, that the base angles of an isosceles triangle are equal, and the theorem still called Thales's theorem, that an angle inscribed in a semicircle is a right angle. [2] He was also said to have measured the height of the Egyptian pyramids from their shadows.
Herodotus reports that Thales predicted a solar eclipse that interrupted a battle between the Lydians and the Medes, an event usually identified with the eclipse of 585 BCE. Modern scholars doubt that the astronomical knowledge available to him could have supported a genuine prediction, and treat the story as an indication of his later reputation rather than a reliable record. [4]
Legacy
Thales became a symbolic figure for the origins of rational enquiry, invoked by philosophers and historians of science from antiquity onward. [1] He died at Miletus, according to tradition in old age. Because the sources are late and anecdotal, contemporary scholarship treats individual claims about him cautiously while retaining his place as the conventional starting point of the Western philosophical and scientific tradition. [3]
