Leucippus is the originator of the famous atomic system which, as recently revived, is held to be the principle of rational science. If we take this system on its own account, it is certainly very barren, and there is not much to be looked for in it; but it must be allowed that we are greatly indebted to Leucippus, because, as it is expressed in our ordinary physics, he separated the universal and the sensuous, or the primary and the secondary, or the essential and the nonessential qualities of body. The universal quality means, in speculative language, the fact that the corporeal is really universally determined through the Notion or the principle of body: Leucippus understood the determinate nature of Being, not in a superficial manner, but in a speculative. When it is said that body has those universal qualities, such as form, impenetrability and weight, we think that the indeterminate conception of body is the essence, and that its essence is something other than these qualities. But speculatively, essential existence is just universal determinations; they are existent in themselves, or the abstract content and the reality of existence. To body as such, there is nothing left for the determination of reality but pure singularity; but it is the unity of opposites, and the unity of these predicates constitutes its reality. Let us recollect that in the Eleatic philosophy Being and non-being were looked at as in opposition; that only Being is, and non-being, in which category we find motion, change, &c., is not. Being is not as yet the unity turning back, and turned back into itself, like Heraclitus’ motion and the universal. It may be said of the point of view that difference, change, motion, &c., fall within sensuous, immediate perception, that the assertion that only Being is, is as contradictory to appearances as to thought; for the nothing, that which the Eleatics abolished, is. Or within the Heraclitean Idea, Being and non-being are the same; Being is, but non-being, since it is one with Being, is as well, or Being is both the predicate of Being and of non-being. But Being and non-being are both expressed as having the qualities of objectivity, or as they are for sensuous perception, and hence they are the opposition of full and empty. Leucippus says this; he expresses as existent what was really present to the Eleatics. Aristotle says (Met. I. 4): “Leucippus and his friend Democritus maintain that the full and the empty are the elements, and they call the one the existent, and the other the non-existent; that is, the full and solid are the existent, the empty and rare, the non-existent. Hence they also say that Being is no more than non-being because the empty is as well as the bodily; and these form the material sources of everything.” The full has the atom as its principle. The Absolute, what exists in and for itself, is thus the atom and the empty (_τὰ ἄτομα καὶ τὸ κενόν_): this is an