The case of the mixture of a smaller quantity with a greater one, such as of a large body with a very small one, leads (the Peripatetics) to consider it impossible that the great body should spread in all the parts of the small one. Where the mixture is not evident, the (Peripatetics) might claim that the smaller body does not unite with all the parts of the greater. When however the mixture is evident, they can explain it by the extension of the masses, although it be very doubtful that a small mass would assume so great an extension, especially when we attribute to the composite body a greater extent, without nevertheless admitting its transformation, as when water transforms itself into air. EVAPORATION MAY LEAD TO A THIRD THEORY OF MIXTURE. 2. What happens when a mass of water transforms itself into air? This question demands particular treatment; for how can the transformed element occupy a greater extension? (We shall not try to explain it on either the Peripatetic or Stoic principles) because we have sufficiently developed above the numerous reasons advanced by both those schools. We had better now consider which of the two systems we ourselves might adopt, and on which side lies reason. Besides, we should consider whether, besides these both, there be not place for a third opinion. REFUTATION OF STOIC EXPLANATION OF EVAPORATION. When water flows through wool, or when paper allows water to filter through it, why does not the whole of the water pass through these substances (without partly remaining within them)? If the water remain therein partially, we shall not be able to unite the two substances or masses. Shall we say that the qualities alone are confused (or, mingled)? Water is not in juxtaposition with the paper, nor is lodged in its pores; for the whole paper is penetrated thereby, and no portion of the matter lacks that quality. If matter be united to quality everywhere, water must everywhere be present in the paper. If it be not water that everywhere is present in the paper, but only (humidity which is) the quality of the water, where then is the water itself? Why is not the mass the same? The matter that has insinuated itself into the paper extends it, and increases its volume. Now this augmentation of volume implies augmentation of mass; and the latter implies that the water has not been absorbed by the book, and that the two substances occupy different places (and do not interpenetrate each other). Since one body causes another to participate in its quality, why would it not also make it participate in its extension? By virtue of this union with a different quality, one quality, united with a different one, cannot, either remain pure, or preserve its earlier nature; it necessarily becomes weaker. But one extension, added to another extension, does not vanish. REFUTATION OF PERIPATETIC EXPLANATION OF EVAPORATION.