121. But, SECONDLY, _there is also void in things_, else they would be jammed together, and unable to move. It is false to say that things may move in a _plenum_: as, when a fish presses on, it leaves room behind it, into which the water may stream; for on what side can the scaly creature move forwards unless the waters have first made room; and on what side can the waters give place so long as the fish cannot move? (This of course is metaphysics, and is altogether absurd. It is the old story of the immovable body receiving the irresistible blow.) Hence there cannot be motion unless there be void to allow of a start. Dripping of water in caves, the passage of food throughout the whole of the body of an animal, the fact that buds and fruit of trees are nourished from the root, voices heard through walls, cold penetrating the very bones, all are proofs that there is void as well as body. Also when one thing is as large as another, but yet lighter, there must be more void in it. 122. THIRD. _There can be no third thing besides body and void._ For if it be to the smallest extent tangible, it is body; if not, it is void. 123. FOURTH. _Bodies are either first beginnings of things_ (atoms), _or a union of such_. Any thing which can be broken or crushed, or which can transmit heat or electricity, is partly body and partly void. Hence body cannot be crushed, and ‘therefore first beginnings are of solid singleness, and in no other way can they have been preserved through ages during infinite time past, in order to reproduce things.’ 124. FIFTH. If there be no limit to breakage, nothing could be reproduced; for reproduction is slower than decay, and therefore the breaking of infinite past ages would have produced a state of things incompatible with the reproduction of anything within finite time. _Hence there exists a least in things._ This cannot be soft, else it would consist partly of void, and be therefore breakable. _First beginnings, then, are strong in solid singleness._ Hence the unreason of those who held fire to be the matter of things, for what surer test can we have than the senses whereby to note truth and falsehood! The doctrine called that of Homœomeria by Anaxagoras is folly,—his notion, to wit, that everything is made up of little parts the same as itself—bones of little bones, flesh of little fleshes, etc. For thus corn and other food, which go to nourish our blood, must be in part composed of blood, and must therefore bleed when crushed by the formidable force of the millstone!