This bridge the atomists undertook to re-establish. They admitted that Ens could not really change--that there could be no real generation, or destruction--no transformation of qualities--no transition of many into one, or of one into many. But they denied the unity and continuity and immobility of Ens: they affirmed that it was essentially discontinuous, plural, and moving. They distinguished the extended, which Parmenides had treated as an _Unum continuum_, into extension with body, and extension without body: into _plenum_ and _vacuum_, matter and space. They conceived themselves to have thus found positive meanings both for Ens and Non-Ens. That which Parmenides called Non-Ens or nothing, was in their judgment the _vacuum_; not less self-existent than that which he called Something. They established their point by showing that Ens, thus interpreted, would become reconcilable to the phenomena of sense: which latter they assumed as their basis to start from. Assuming motion as a phenomenal fact, obvious and incontestable, they asserted that it could not even appear to be a fact, without supposing _vacuum_ as well as body to be real: and the proof that both of them were real was, that only in this manner could sense and reason be reconciled. Farther, they proved the existence of a _vacuum_ by appeal to direct physical observation, which showed that bodies were porous, compressible, and capable of receiving into themselves new matter in the way of nutrition. Instead of the Parmenidean Ens, one and continuous, we have a Demokritean Ens, essentially many and discontinuous: _plena_ and _vacua_, spaces full and spaces empty, being infinitely intermingled.[203] There existed atoms innumerable, each one in itself essentially a plenum, admitting no vacant space within it, and therefore indivisible as well as indestructible: but each severed from the rest by surrounding vacant space. The atom could undergo no change: but by means of the empty space around, it could freely move. Each atom was too small to be visible: yet all atoms were not equally small; there were fundamental differences between them in figure and magnitude: and they had no other qualities except figure and magnitude. As no atom could be divided into two, so no two atoms could merge into one. Yet though two or more atoms could not so merge together as to lose their real separate individuality, they might nevertheless come into such close approximation as to appear one, and to act on our senses as a phenomenal combination manifesting itself by new sensible properties.[204] [Footnote 203: It is chiefly in the eighth chapter of the treatise De Gener. et Corr. (i. 8) that Aristotle traces the doctrine of Leukippus as having grown out of that of the Eleates. [Greek: Leu/kippos d' e)/chein ô)|ê/thê lo/gous, oi(/tines pro\s tê\n ai)/sthêsin o(mologou/mena le/gontes ou)k a)nairê/sousin ou)/te ge/nesin ou)/te phthora\n ou)/te ki/nêsin kai\ to\ plê=thos tô=n o)/ntôn], &c.