Empedocles

Empedocles of Acragas (c. 494 – 434 BCE) was a physician, a democrat, a poet and, by his own account, something close to a god. His two poems, On Nature and Purifications, survive in longer fragments than any other early philosopher's work, and the legend that he ended his life by leaping into the crater of Etna has outlasted most of his arguments.

Four roots

His lasting contribution is the doctrine of four elements, which he called roots: fire, air, water and earth. Each is eternal and unchanging, as Parmenides required of what truly is; what we call birth and death is only their mixing and separation. Bone, for instance, is earth, water and fire in fixed proportion. The elements themselves neither come to be nor pass away.

Love and Strife

Two forces act on the roots. Love draws unlike things together into mixtures; Strife pulls them apart into pure masses. The cosmos runs in a cycle. Under the full rule of Love the elements are blended into a single sphere; Strife enters and divides them; at the extreme of Strife they lie in four separate layers; then Love returns. Worlds like ours exist only in the two intermediate phases, where mixture and separation are both under way.

There is no birth of any mortal thing, nor any end in wretched death, but only mixing and exchange of what is mixed.

Biology and perception

• In the age of Love's advance, separate limbs and organs wandered about and joined at random; only the viable combinations survived.
• Perception works by effluences: every object sheds thin films that enter the pores of the sense organs, and like is known by like.
• Breathing he explained by the clepsydra, the water-lifter, showing that air is a body and not empty space.

The exile of the soul

The Purifications tell a different story in a religious register: a spirit that trusted in Strife is banished for thirty thousand seasons to wander through every form of mortal life. Empedocles claims to have been a boy, a girl, a bush, a bird and a fish. Abstinence from animal flesh is the discipline that shortens the exile. Whether the two poems form one system or two is still argued; the fragments allow both readings.