48 On Quantity According to the Common Opinion
On Quantity According to the Common Opinion in the other categories is said to be cqual or unequal per se, but only per accidens. He implies this when he says, "But of the things that are not quantities" (supply: per se) " 'equal' and 'unequal' do not seem to be said much," because of these things 'equal' and 'unequal' are not said per se, but only per accidens. But this is perfectly compatible with the claim that 'equal' and 'unequal' are said of other things, and in the same way 'quantity' is predicated of these other things.
48: On Quantity According to the Common Opinion Things are quite different in the view which construes quantity as an absolute thing distinct from substance and quality, and the point, the line, the surface, and the solid as things different from each other. On that view dimensions are things informing substance and sustaining corporeal qualities.
Thus, substance is not dimension, but the subject of dimension, nor is quality dimension, but a thing subjectively existing in dimension. Now quantity either has parts which are joined at some common boundary or it does not. If it does, then those parts are all permanent and they are extended according to length in which case we have the line; or they are extended according to both length and breadth and we have the surface; or they are extended according to length, breadth, and depth and we have the solid.
But many who hold this view construe place as something really identical with surface. But if not all the parts of this kind of quantity are permanent, we have time. If on the other hand the parts are not joined at any common boundary, they are either permanent in which case we have number; or they are not permanent in which case we have speech. Thus, the genus of quantity contains the line, the surface, the solid, place, time, number, and speech.
But the point, with the instant and unity, does not fall under the genus of quantity per se but only be reduction.
Quantities also are divided into those whose parts have relative position (the species here are the line, the surface, the solid, and place) and those whose parts have no such relative position (the species here are time, number, and speech).
The first property of quantity is that it has no contrary; for although the quality subjectively existing in quantity has a contrary, quantity itself has no contrary. This is clear from induction.