I think enough has been said on the supposition that we should believe
that the body which Christ received was not taken from Mary. But if it
was taken from Mary and the human and divine natures did not continue,
each in its perfection, this may have happened in one of three ways.
Either Godhead was translated into manhood, or manhood into Godhead, or
both were so modified and mingled that neither substance kept its proper
form. But if Godhead was translated into manhood, that has happened
which piety forbids us to believe, viz. while the manhood continued in
unchangeable substance Godhead was changed, and that which was by nature
passible and mutable remained immutable, while that which we believe to
be by nature immutable and impassible was changed into a mutable thing.
This cannot happen on any show of reasoning. But perchance the human
nature may seem to be changed into Godhead. Yet how can this be if
Godhead in the conception of Christ received both human soul and body?
Things cannot be promiscuously changed and interchanged. For since some
substances are corporeal and others incorporeal, neither can a corporeal
substance be changed into an incorporeal, nor can an incorporeal be
changed into that which is body, nor yet incorporeals interchange their
proper forms; for only those things can be interchanged and transformed
which possess the common substrate of the same matter, nor can all of
these so behave, but only those which can act upon and be acted on by
each other. Now this is proved as follows: bronze can no more be
converted into stone than it can be into grass, and generally no body
can be transformed into any other body unless the things which pass into
each other have a common matter and can act upon and be acted on by each
other, as when wine and water are mingled both are of such a nature as
to allow reciprocal action and influence. For the quality of water can
be influenced in some degree by that of wine, similarly the quality of
wine can be influenced by that of water. And therefore if there be a
great deal of water but very little wine, they are not said to be
mingled, but the one is ruined by the quality of the other. For if you
pour wine into the sea the wine is not mingled with the sea but is lost
in the sea, simply because the quality of the water owing to its bulk
has been in no way affected by the quality of the wine, but rather by
its own bulk has changed the quality of the wine into water. But if the
natures which are capable of reciprocal action and influence are in
moderate proportion and equal or only slightly unequal, they are really
mingled and tempered by the qualities which are in moderate relation to
each other. This indeed takes place in bodies but not in all bodies, but
only in those, as has been said, which are capable of reciprocal action
and influence and have the same matter subject to their qualities. For
all bodies which subsist in conditions of birth and decay seem to
possess a common matter, but all bodies are not capable of reciprocal
action and influence. But corporeals cannot in any way be changed into
incorporeals because they do not share in any common underlying matter
which can be changed into this or that thing by taking on its qualities.
For the nature of no incorporeal substance rests upon a material basis;
but there is no body that has not matter as a substrate. Since this is
so, and since not even those things which naturally have a common matter
can pass over into each other unless they have the power of acting on
each other and being acted upon by each other, far more will those
things not suffer interchange which not only have no common matter but
are different in substance, since one of them, being body, rests on a
basis of matter, while the other, being incorporeal, cannot possibly
stand in need of a material substrate.
It is therefore impossible for a body to be changed into an incorporeal
species, nor will it ever be possible for incorporeals to be changed
into each other by any process of mingling. For things which have no
common matter cannot be changed and converted one into another. But
incorporeal things have no matter; they can never, therefore, be changed
about among themselves. But the soul and God are rightly believed to be
incorporeal substances; therefore the human soul has not been converted
into the Godhead by which it was assumed. But if neither body nor soul
can be turned into Godhead, it could not possibly happen that manhood
should be transformed into God. But it is much less credible that the
two should be confounded together since neither can incorporality pass
over to body, nor again, contrariwise, can body pass over into
incorporality when these have no common matter underlying them which can
be converted by the qualities of one of two substances.
But the Eutychians say that Christ consists indeed of two natures, but
not in two natures, meaning, no doubt, thereby, that a thing which
consists of two elements can so far become one, that the elements of
which it is said to be made up disappear; just as, for example, when
honey is mixed with water neither remains, but the one thing being
spoilt by conjunction with the other produces a certain third thing, so
that third thing which is produced by the combination of honey and water
is said to consist of both, but not in both. For it can never consist in
both so long as the nature of both does not continue. For it can consist
of both even though each element of which it is compounded has been
spoiled by the quality of the other; but it can never consist in both
natures of this kind since the elements which have been transmuted into
each other do not continue, and both the elements in which it seems to
consist cease to be, since it consists of two things translated into
each other by change of qualities.
But Catholics in accordance with reason confess both, for they say that
Christ consists both of and in two natures. How this can be affirmed I
will explain a little later. One thing is now clear; the opinion of
Eutyches has been confuted on the ground that, although there are three
ways by which the one nature can subsist of the two, viz. either the
translation of divinity into humanity or of humanity into divinity or
the compounding of both together, the foregoing train of reasoning
proves that no one of the three ways is a possibility.