Chapter 63 — Solution of the foregoing difficulties, and first with regard to the changing of the bread into Christ’s body

Although the operation of the divine power in this sacrament is too sublime and hidden for human research, lest unbelievers should deem the teaching of the Church on this question to be impossible, we must endeavor to show that it involves no impossibility whatsoever.

The first point to consider, then, is how Christ’s body begins to be present under this sacrament.

It is, in fact, impossible for this to take place by local movement of Christ’s body. This is because it would follow that it ceases to be in heaven whenever this sacrament is enacted; and because then this sacrament could only be celebrated in one place at a time, since the same local movement cannot terminate in more than one place; and because local movement cannot be instantaneous but needs time, whereas the consecration is effective in the last instant of the pronouncement of the words.

It remains, therefore, to be said that the true body of Christ begins to be present in this sacrament through the substance of the bread being changed into the substance of his body, and the substance of the wine into the substance of his blood.

Hence we see how false are the opinions of those who say that in this sacrament the substance of the bread exists together with the substance of Christ’s body, as well as the opinion of those who say that the substance of the bread is annihilated, or that it is reduced to prime matter. In either case it follows that, in this sacrament, Christ’s body begins to be present by local movement, and we have proved this to be impossible.

Moreover, if the substance of the bread is present in this sacrament together with Christ’s body, he should have said: Here is my body, rather than: This is my body, because ‘here’ points to the substance seen, which would be the substance of bread if it remains in this sacrament together with Christ’s body.

Likewise, it is seemingly impossible that the substance of the bread be wholly annihilated. It would follow that a considerable portion of matter originally created has returned into nothingness on account of the frequent celebration of this mystery. Nor is it becoming that the divine power should annihilate anything in the sacrament of salvation. It is impossible for the substance of the bread to be reduced to prime matter, since prime matter cannot exist without a form. Perhaps prime matter could be taken to signify the elementary bodies; but then, if the substance of the bread is resolved into these, this would be perceptible to the senses of necessity, since the corporeal elements are objects of sense. Moreover, this would involve local change and the corporeal alteration of contraries, which cannot occur instantaneously.

It must, however, be observed that this changing of the bread into Christ’s body is brought about in a manner different from all natural changes. In all natural changes, the subject remains, in which various forms succeed one another. And these forms may be either accidental—as when white is changed into black—or substantial—as when air is changed into fire. Hence these are called formal changes. But in the aforesaid change, one subject passes into another, and the accidents remain: hence this is called a substantial change. How and why these accidents remain, we shall discuss later on.

At present we have to inquire how one subject is changed into another, since nature cannot do this. For every work of nature presupposes matter, whereby subjects are individualized, so that nature cannot make this substance to be that substance (for instance, that this finger be that finger). But matter is subject to the divine power, since by it was it brought into being. Hence it is possible, by the divine power, for this or that individual substance to be changed into this or that already existing substance. For just as by the power of a natural agent, whose operation does not go beyond the changing of a form in an already existing subject, the whole of one thing is changed into the whole of another by a change of species or form (for instance, this air into this already kindled fire), so by the power of God, which presupposes no matter but produces it, this matter is changed into that matter. Consequently, this individual is chaged into that, for matter is the principle of individuality just as form is the principle of the species.

Now it is clear that in the aforesaid change of the bread into Christ’s body there is no common subject remaining after the change, seeing that a change is wrought of the first subject, which is the principle of individuality. And yet something must remain, in order that it should be true to say: This is my body (which words both signify and effect this change). And since, as we have proved, neither the substance of the bread, nor any prior matter remains, it follows that there remains that which is besides the substance of the bread, namely, that which is accidental to it. Therefore, the accidents of the bread remain even after the aforesaid change.

Among these accidents a certain order is to be noted. Of all accidents, dimensive quantity adheres most closely to substance; afterwards, with quantity as a medium, the substance is affected with qualities (for instance, with color by means of the surface). Hence the division of the other accidents is incidental to the division of quantity. Further, qualities are the principles of actions and passions, as well as of certain relationships (for instance of father and son, master and servant, and so on); while some relationships are founded immediately on quantity (for instance greater and lesser, double and half, and the like). Accordingly, after the aforesaid change, the accidents of the bread must be said to remain in such a way that dimensive quantity alone remains without a subject, while the qualities are founded on it as their subject, and consequently actions, passions, and relations also. Therefore, in this change, the contrary happens to that which is the rule in natural transmutations, where the substance remains as the subject of change, while the accidents are changed. But here, on the contrary, accident remains and subject passes away.

This change cannot, properly speaking, be described as a movement in the physical sense, which requires a subject: it is a kind of sequence of substances, just as in creation existence follows nonexistence, as stated above. (Bk. 2, ch. 19.)

This, then, is one reason why the accident of the bread must remain, so that something may be found to remain in the aforesaid change.

But there is yet another necessary reason. If the substance of the bread be changed into Christ’s body, and the accidents of the bread pass away, the result of such a change would be that Christ’s body, in its substance, is not where the bread was before, since Christ’s body would bear no relation to that place. On the other hand, after the change, the dimensive quantity whereby the bread occupied that place remains, while the substance of the bread is changed into Christ’s body, which thus comes to be under the dimensive quantity of the bread, and consequently occupies the place of the bread. This is, however, by means of the bread’s dimensions.

Other reasons might be assigned: from the point of view of faith, which is of things invisible; or from the point of view of merit, which is so much greater as this sacrament is more invisibly enacted (for Christ’s body is hidden under the accidents of bread). Also, with a view to a more commodious and fitting use of this sacrament, for it would indeed be revolting to the partakers, and repulsive to the beholders, if the faithful received Christ’s body under its own form. For these reasons, Christ’s body is offered as meat, and his blood as drink, under the appearance of bread and wine, which are man’s most common form of meat and drink.