Empedocles

[person]

Greek philosopher born in Acragas (490-430 BCE). He is credited (by Aristotle) with inventing rhetoric, and by the philosopher Galen with founding the science of medicine. Empedocles is remembered for his belief that all matter was composed of four elements: earth, air, fire, and water. He also proved experimentally that air was a substance, rather than empty space, and deduced that light travels at a finite velocity.