Pythagoras (c.580 - 500 BCE) Greek philosopher, sage and mathematician. He founded a mystical and secretive cult which had an inner circle of followers known as mathematikoi. His whole life is shrouded by myth and legend. He left no written works. To Pythagoras, ???ll things are numbers?? his achievements in mathematical discoveries arise from his fundamental beliefs about the understanding and representation of the world of nature through numbers. An important figure in the development of mathematics and astronomy, he was introduced to mathematical ideas by the philosophers Thales and Animaxander, in astronomy he was influenced by the Babylonians. He introduced the Pythagorean Theory of right-angled triangles, the mathematical relationship between notes on the musical scale, the concept of irrational numbers and the numerical relationships concerning the orbits of celestial bodies.