Legend had much to say about Empedocles. He was supposed to have worked miracles, or what seemed such, sometimes by magic, sometimes by means of his scientific knowledge. He could control the winds, we are told; he restored to life a woman who had seemed dead for thirty days; finally, it is said, he died by leaping into the crater of Etna to prove that he was a god. In the words of the poet:
Great Empedocles, that ardent soul Leapt into Etna, and was roasted whole.
...His most important contribution to science was his discovery of air as a separate substance. This he proved by the observation that when a bucket or any similar vessel is put upside down into water, the water does not enter into the bucket. He says:
"When a girl, playing with a water-clock of shining brass, puts the orifice of the pipe upon her comely hand, and dips the waterclock into the yielding mass of silvery water, the stream does not then flow into the vessel, but the bulk of the air inside, pressing upon the close-packed perforations, keeps it out till she uncovers the compressed stream; but then air escapes and an equal volume of water runs in."
This passage occurs in an explanation of respiration.
He also discovered at least one example of centrifugal force: that if a cup of water is whirled round at the end of a string, the water does not come out.
He knew that there is sex in plants, and he had a theory (somewhat fantastic, it must be admitted) of evolution and the survival of the fittest. Originally, "countless tribes of mortal creatures were scattered abroad endowed with all manner of forms, a wonder to behold." There were heads without necks, arms without shoulders, eyes without foreheads, solitary limbs seeking for union. These things joined together as each might chance; there were shambling creatures with countless hands, creatures with faces and breasts looking in different directions, creatures with the bodies of oxen and the faces of men, and others with the faces of oxen and the bodies of men. There were hermaphrodites combining the natures of men and women, but sterile. In the end, only certain forms survived.
As regards astronomy: he knew that the moon shines by reflected light, and thought that this is also true of the sun; he said that light takes time to travel, but so little time that we cannot observe it; he knew that solar eclipses are caused by the interposition of the moon, a fact which he seems to have learnt from Anaxagoras.
He was the founder of the Italian school of medicine, and the medical school which sprang from him influenced both Plato and Aristotle. According to Burnet, it affected the whole tendency of scientific and philosophical thinking.
All this shows the scientific vigour of his time, which was not equalled in the later ages of Greece.
I come now to his cosmology. It was he... who established earth, air, fire, and water as the four elements (though the word "element" was not used by him). Each of these was everlasting, but they could be mixed in different proportions, and thus produce the changing complex substances that we find in the world. They were combined by Love and separated by Strife. Love and Strife were, for Empedocles, primitive substances on a level with earth, air, fire, and water. There were periods when Love was in the ascendant, and others when Strife was the stronger. There had been a golden age when Love was completely victorious. In that age, men worshipped only the Cyprian Aphrodite. The changes in the world are not governed by any purpose, but only by Chance and Necessity. There is a cycle: when the elements have been thoroughly mixed by Love, Strife gradually sorts them out again; when Strife has separated them, Love gradually reunites them. Thus every compound substance is temporary; only the elements, together with Love and Strife, are everlasting.
...Empedocles held that the material world is a sphere; that in the Golden Age Strife was outside and Love inside; then, gradually, Strife entered and Love was expelled, until, at the worst, Strife will be wholly within and Love wholly without the sphere. Then—though for what reason is not clear—an opposite movement begins, until the Golden Age returns, but not for ever. The whole cycle is then repeated. One might have supposed that either extreme could be stable, but that is not the view of Empedocles. He wished to explain motion while taking account of the arguments of Parmenides, and he had no wish to arrive, at any stage, at an unchanging universe.
The History of Western Philosophy, Bertrand Russell, Chapter 6