Empedocles’ The Testimonia, Volume II

Alexander of Aphrodisias, Questions

But one might ask — even granting the doctrine of effluences — why on earth the stone does not follow its own effluences, whereas the iron moves toward it. For nothing in what has been said makes the stone move toward the iron any more than the iron toward the stone. Again, why does the iron not sometimes move toward something else, without the stone present, when its own effluences travel out in a mass? Why can the effluences of the stone alone move the air that caps the passages of the iron and holds the effluences back? And again, why does nothing else travel toward anything else in this way, although he says of many things that their passages are commensurate with the effluences? At any rate he says: "water …"

Report, very likely from a lost work of Theophrastus, with the reporter's own criticism.

This is the earliest surviving theory of magnetism, and it is an achievement of a particular kind: Empedocles refuses to treat attraction as a sympathy or an occult power and insists on a mechanism made of the same stuff as everything else. Alexander's four objections are all good ones, and the first is devastating — the account is symmetrical, and gives no reason why the iron should move rather than the stone. That difficulty would not be answered for two thousand years.

Bearing on Volume I. B 91, where oil and water are said not to mix, is the fragment Alexander cites; the pore doctrine is A 87.

25 ταύτης from the apographs: τούτου in V. — 34 αὐτῆς in V, corrected by Apelt. — 38 πρὸς ἄλληλα is deleted by Kranz; λέγεις in V, corrected by Spengel. The quotation is fragment B 91.