Thales of Miletus

Thales of Miletus was a Greek thinker of the early sixth century BC, regarded as the first known Greek philosopher, scientist and mathematician, although his own occupation was that of an engineer. He founded the Milesian school of natural philosophy and is believed to have taught Anaximander. None of his writing survives, so what is said of his mathematics rests on later reports, chiefly Proclus, who credits him with bringing geometry from Egypt to Greece. Five propositions of elementary geometry are traditionally attributed to him: that a circle is bisected by a diameter, that the base angles of an isosceles triangle are equal, that vertically opposite angles are equal, that triangles with two angles and one side equal are congruent, and that an angle in a semicircle is a right angle. Reports also say he predicted the solar eclipse of 585 BC and found the height of pyramids from their shadows.