2. About the Second Change

386. About the second change too it is manifest that the same quantity remains there and can, according to the common opinion, be the subject of the alteration, such that the quality in flux has the same quantity for its subject that the abiding quality is posited as having. And such change is, as to genus, either according to difference in shape, or according to difference in quality (of the third species [sc. sense qualities]) as to more and less; and this variation as to more and less does not destroy the accidents in the Eucharist insofar as they are necessary for the Eucharist (variation that destroys the Eucharist will be spoken of in what follows [q.2 nn.432-439]).

387. As to difference of shape, it would seem that it would destroy the quantity, according to the remark of Avicenna in his Metaphysics [II ch.2] that difference of dimension requires difference of quantity.

388. But this seems to be contrary to the senses, for it would be too hard to say that water would, as often as it was differently configured in different vessels, as often have a simply new quantity, even though the parts remained the same in themselves and in the whole. Configuration, therefore, only states, over and above quantity, a relation of parts to each other or of the limits that include the parts; but this relation can be changed while the parts remain the same in themselves and in the whole.

389. About quality of the third species too it is sufficiently manifest that, when the species remains the same through the whole motion, the quantity remains the same.