Thales of Miletus. Historical portrait of the Ancient Greek philosopher, mathematician and astronomer Thales (c.625-550 BC). He is believed to be the first identifiable scientist and the founder of Greek philosophy, but little is known about him. He is reported to have measured the height of a pyramid from its shadow and to have predicted a solar eclipse in 585 BC. Later philosophers recorded his belief that everything was water - the first recorded general physical principle - and that the Earth was a disc floating in a vast ocean. He also attempted to provide natural explanations for earthquakes, rather than ascribing them to supernatural causes.