Empedocles (ĕmpĕdˈəklēz) [key], c.495–c.435 B.C., Greek philosopher, b. Acragas (present Agrigento), Sicily. Leader of the democratic faction in his native city, he was offered the crown, which he refused. A turn in political fortunes drove him and his followers into exile. Empedocles taught that everything in existence is composed of four underived and indestructible roots, material particles identified as fire, water, earth, and air. He declared the atmosphere to be a corporeal substance, not a mere void; and in the absence of the void or empty space he explained motion as the interpenetration of particles, under the alternating action of two forces, harmony and discord. Believing that motion, or change of place, is the only sort of change possible, he explained all apparent changes in quality or quantity as changes of position of the basic particles underlying the observable object. He was thereby the first to state a principle that is now central to physics.
See studies by C. E. Millerd (1980) and M. R. Wright (1981).