REFUTATION OF THE STOICS.
We now pass to the opinions of (Zeno and the other Stoic) philosophers,[61] who assert that two bodies which make up a mixture mutually interpenetrate each other totally. They support this view by observing that when the bodies interpenetrate totally, they are divided without the occurrence of a continuous division (which would make their molecules lose their magnitude). Indeed, perspiration issues from the human body without its being divided or riddled with holes. To this it may be objected that nature may have endowed our body with a disposition to permit perspiration to issue easily. To this (the Stoics) answer that certain substances (like ivory[62]), which when worked into thin sheets, admit, in all their parts, a liquid (oat-gruel) which passes from one surface to the other. As these substances are bodies, it is not easy to understand how one element can penetrate into another without separating its molecules. On the other hand, total division must imply mutual destruction (because their molecules would lose all magnitude whatever). When, however, two mingled bodies do not together occupy more space than either of them separately (the Stoics) seem forced to admit to their adversaries that this phenomenon is caused by the displacement of air.