Termed the Pythagorean theorem
In the late 6th Century BC, the great Ionian Greek philosopher, mathematician, and founder of a religious society, made an amazing discovery in geometry that bears his name to the present day, termed the Pythagorean theorem.
Most of the information about him was written down centuries after he lived, so that many of the accomplishments he is credited with may actually have been accomplishments of his colleagues and successors. Nevertheless the Pythagorean ideas had a significant influence on Plato, and through him, on all of Western philosophy.
It is said that Pythagoras was the first man to call himself a philosopher, a lover of wisdom. This means that his famous work, the Pythagorean theorem, is more than just a discovery in geometry, but involves a form of science that enables one to understand aspects of truth that are hidden from the senses, but can be recognized in the mind to be absolutely truthful, and this without the aid of mathematics.