Whether Bread Can Be Converted into the Body of Christ?
Objection 1: It seems that bread cannot be converted into the body of
Christ. For conversion is a kind of change. But in every change there
must be some subject, which from being previously in potentiality is
now in act. because as is said in _Phys._ iii: "motion is the act of
a thing existing in potentiality." But no subject can be assigned for
the substance of the bread and of the body of Christ, because it is
of the very nature of substance for it "not to be in a subject," as
it is said in _Praedic._ iii. Therefore it is not possible for the
whole substance of the bread to be converted into the body of Christ.
Obj. 2: Further, the form of the thing into which another is
converted, begins anew to inhere in the matter of the thing converted
into it: as when air is changed into fire not already existing, the
form of fire begins anew to be in the matter of the air; and in like
manner when food is converted into non-pre-existing man, the form of
the man begins to be anew in the matter of the food. Therefore, if
bread be changed into the body of Christ, the form of Christ's body
must necessarily begin to be in the matter of the bread, which is
false. Consequently, the bread is not changed into the substance of
Christ's body.
Obj. 3: Further, when two things are diverse, one never becomes the
other, as whiteness never becomes blackness, as is stated in _Phys._
i. But since two contrary forms are of themselves diverse, as being
the principles of formal difference, so two signate matters are of
themselves diverse, as being the principles of material distinction.
Consequently, it is not possible for this matter of bread to become
this matter whereby Christ's body is individuated, and so it is not
possible for this substance of bread to be changed into the substance
of Christ's body.
_On the contrary,_ Eusebius Emesenus says: "To thee it ought neither
to be a novelty nor an impossibility that earthly and mortal things
be changed into the substance of Christ."
_I answer that,_ As stated above (A. 2), since Christ's true body is
in this sacrament, and since it does not begin to be there by local
motion, nor is it contained therein as in a place, as is evident from
what was stated above (A. 1, ad 2), it must be said then that it
begins to be there by conversion of the substance of bread into
itself.
Yet this change is not like natural changes, but is entirely
supernatural, and effected by God's power alone. Hence Ambrose says
[(De Sacram. iv): "See how Christ's word changes nature's laws, as He
wills: a man is not wont to be born save of man and woman: see
therefore that against the established law and order a man is born of
a Virgin": and] [*The passage in the brackets is not in the Leonine
edition] (De Myster. iv): "It is clear that a Virgin begot beyond the
order of nature: and what we make is the body from the Virgin. Why,
then, do you look for nature's order in Christ's body, since the Lord
Jesus was Himself brought forth of a Virgin beyond nature?"
Chrysostom likewise (Hom. xlvii), commenting on John 6:64: "The words
which I have spoken to you," namely, of this sacrament, "are spirit
and life," says: i.e. "spiritual, having nothing carnal, nor natural
consequence; but they are rent from all such necessity which exists
upon earth, and from the laws here established."
For it is evident that every agent acts according as it is in act.
But every created agent is limited in its act, as being of a
determinate genus and species: and consequently the action of every
created agent bears upon some determinate act. Now the determination
of every thing in actual existence comes from its form. Consequently,
no natural or created agent can act except by changing the form in
something; and on this account every change made according to
nature's laws is a formal change. But God is infinite act, as stated
in the First Part (Q. 7, A. 1; Q. 26, A. 2); hence His action extends
to the whole nature of being. Therefore He can work not only formal
conversion, so that diverse forms succeed each other in the same
subject; but also the change of all being, so that, to wit, the whole
substance of one thing be changed into the whole substance of
another. And this is done by Divine power in this sacrament; for the
whole substance of the bread is changed into the whole substance of
Christ's body, and the whole substance of the wine into the whole
substance of Christ's blood. Hence this is not a formal, but a
substantial conversion; nor is it a kind of natural movement: but,
with a name of its own, it can be called "transubstantiation."
Reply Obj. 1: This objection holds good in respect of formal change,
because it belongs to a form to be in matter or in a subject; but it
does not hold good in respect of the change of the entire substance.
Hence, since this substantial change implies a certain order of
substances, one of which is changed into the other, it is in both
substances as in a subject, just as order and number.
Reply Obj. 2: This argument also is true of formal conversion or
change, because, as stated above (ad 1), a form must be in some
matter or subject. But this is not so in a change of the entire
substance; for in this case no subject is possible.
Reply Obj. 3: Form cannot be changed into form, nor matter into
matter by the power of any finite agent. Such a change, however, can
be made by the power of an infinite agent, which has control over all
being, because the nature of being is common to both forms and to
both matters; and whatever there is of being in the one, the author
of being can change into whatever there is of being in the other,
withdrawing that whereby it was distinguished from the other.
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