286 upward, but to the extent it is heavy, it helps motion downward, have given form to another argument, saying: Air, because it carries heavy things downward more easily, helps downward motion more than upward motion, because it carries light things upward with more difficulty.They have concluded that air must necessarily be deemed heavy in its own region. However, it will soon be known that this is entirely false: and we will demonstrate that air and water in their own region are neither heavy nor light; {1} we will subsequently demonstrate that the argument of the more recent philosophers leads to a conclusion purely and simply the opposite of that which they laboriously try to prove, and that they could not have found an argument which is more at variance with themselves.
And, to begin with, it seems entirely inconceivable how air and water exert weight in their proper place. For any portion of water in the place of air, that is in air itself, exerts weight, and indeed is carried downward because it exerts weight; but who will ever conceive that a part of water goes down in water? For if it goes down, when it will be at the bottom, it is necessary that the place, into which it enters, be then evacuated by the other water, which will be forced to go up to where the other has receded from; and thus this portion of water will then be light in its own place. Secondly, if any portion of water is heavy in water, let it be called, for example, a: hence since the portion of water a in water is heavy and goes down, if we then take another portion of water which is equal in size to this same a, a will necessarily be heavier than this portion of water, and thus water will be heavier than water: what more foolish thing could be imagined? And to Aristotle's example concerning the bladder, I answer that, if the opening of the inflated bladder or bag is opened, in such a way that air is retained in the bag, not compressed by force, then the bladder will not be heavier than when not inflated: but if much air is compressed by force in it, who will doubt that it will exert weight?For the air, condensed by force, is heavier than free, roaming air: just as if a bladder is filled with wool, but then another equal quantity of wool is added, compressing it by force, who will be so irresolute as to doubt whether or not the bladder will become heavier?