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.