At any rate Love often differentiates and Strife combines: because whenever the universe is differentiated into its elements by Strife, fire and each of the other elements are agglomerated into a unity; and whenever they are all combined together again by Love, the particles of each element are necessarily again differentiated. Empedocles, then, differed from his predecessors in that he first introduced the division of this cause, making the source of motion not one but two contrary forces. Further, he was the first to maintain that the so-called material elements are four—not that he uses them as four, but as two only, treating fire on the one hand by itself, and the elements opposed to it—earth, air and water—on the other, as a single nature. Cf. 3.14. This can be seen from a study of his writings. e.g. Empedocles, Fr. 62 (Diels) . Such, then, as I say, is his account of the nature and number of the first principles. Leucippus, Of Miletus ; fl. circa 440 (?) B.C. See Burnet, E.G.P. 171 ff. however, and his disciple Democritus Of Abdera ; fl. circa 420 B.C. E.G.P loc. cit. hold that the elements are the Full and the Void—calling the one what is and the other what is not. Of these they identify the full or solid with what is, and the void or rare with what is not (hence they hold that what is not is no less real than what is, For the probable connection between the Atomists and the Eleatics see E.G.P. 173, 175, and cf. De Gen. et Corr. 324b 35-325a 32 . because Void is as real as Body); and they say that these are the material causes of things. And just as those who make the underlying substance a unity generate all other things by means of its modifications, assuming rarity and density as first principles of these modifications, so these thinkers hold that the differences i.e., of the atoms. are the causes of everything else.