Reply Obj. 1: The manner of being of every thing is determined by what belongs to it of itself, and not according to what is coupled accidentally with it: thus an object is present to the sight, according as it is white, and not according as it is sweet, although the same object may be both white and sweet; hence sweetness is in the sight after the manner of whiteness, and not after that of sweetness. Since, then, the substance of Christ's body is present on the altar by the power of this sacrament, while its dimensive quantity is there concomitantly and as it were accidentally, therefore the dimensive quantity of Christ's body is in this sacrament, not according to its proper manner (namely, that the whole is in the whole, and the individual parts in individual parts), but after the manner of substance, whose nature is for the whole to be in the whole, and the whole in every part.
Reply Obj. 2: Two dimensive quantities cannot naturally be in the same subject at the same time, so that each be there according to the proper manner of dimensive quantity. But in this sacrament the dimensive quantity of the bread is there after its proper manner, that is, according to commensuration: not so the dimensive quantity of Christ's body, for that is there after the manner of substance, as stated above (ad 1).
Reply Obj. 3: The dimensive quantity of Christ's body is in this sacrament not by way of commensuration, which is proper to quantity, and to which it belongs for the greater to be extended beyond the lesser; but in the way mentioned above (ad 1, 2). _______________________
FIFTH ARTICLE [III, Q. 76, Art. 5]
Whether Christ's Body Is in This Sacrament As in a Place?
Objection 1: It seems that Christ's body is in this sacrament as in a place. Because, to be in a place definitively or circumscriptively belongs to being in a place. But Christ's body seems to be definitively in this sacrament, because it is so present where the species of the bread and wine are, that it is nowhere else upon the altar: likewise it seems to be there circumscriptively, because it is so contained under the species of the consecrated host, that it neither exceeds it nor is exceeded by it. Therefore Christ's body is in this sacrament as in a place.
Obj. 2: Further, the place of the bread and wine is not empty, because nature abhors a vacuum; nor is the substance of the bread there, as stated above (Q. 75, A. 2); but only the body of Christ is there. Consequently the body of Christ fills that place. But whatever fills a place is there locally. Therefore the body of Christ is in this sacrament locally.
Obj. 3: Further, as stated above (A. 4), the body of Christ is in this sacrament with its dimensive quantity, and with all its accidents. But to be in a place is an accident of a body; hence "where" is numbered among the nine kinds of accidents. Therefore Christ's body is in this sacrament locally.
On the contrary, The place and the object placed must be equal, as is clear from the Philosopher (Phys. iv). But the place, where this sacrament is, is much less than the body of Christ. Therefore Christ's body is not in this sacrament as in a place.
I answer that, As stated above (A. 1, ad 3; A. 3), Christ's body is in this sacrament not after the proper manner of dimensive quantity, but rather after the manner of substance. But every body occupying a place is in the place according to the manner of dimensive quantity, namely, inasmuch as it is commensurate with the place according to its dimensive quantity. Hence it remains that Christ's body is not in this sacrament as in a place, but after the manner of substance, that is to say, in that way in which substance is contained by dimensions; because the substance of Christ's body succeeds the substance of bread in this sacrament: hence as the substance of bread was not locally under its dimensions, but after the manner of substance, so neither is the substance of Christ's body. Nevertheless the substance of Christ's body is not the subject of those dimensions, as was the substance of the bread: and therefore the substance of the bread was there locally by reason of its dimensions, because it was compared with that place through the medium of its own dimensions; but the substance of Christ's body is compared with that place through the medium of foreign dimensions, so that, on the contrary, the proper dimensions of Christ's body are compared with that place through the medium of substance; which is contrary to the notion of a located body.