Thales of Miletus

Thales of Miletus was a pre-Socratic Greek philosopher who lived roughly 626 to 545 BC in Ionia and is counted among the Seven Sages of ancient Greece, often called the first philosopher in the Greek tradition for using natural explanation and deductive reasoning rather than myth to account for the world. He held that water was the fundamental substance underlying all things, and in mathematics and astronomy he is credited with developing early geometric theorems, including the result now called Thales theorem about right triangles inscribed in circles, calculating the height of pyramids from their shadows, predicting a solar eclipse in 585 BC, and observing the position of the constellation Ursa Minor.