y of the union of the
two natures in Christ. The first confused the natures, as Eutyches
and Dioscorus, who held that from the two natures one nature
resulted, so that they confessed Christ to be "from" two natures
(which were distinct before the union), but not "in" two natures (the
distinction of nature coming to an end after the union). The second
was the heresy of Nestorius and Theodore of Mopsuestia, who separated
the persons. For they held the Person of the Son of God to be
distinct from the Person of the Son of man, and said these were
mutually united: first, "by indwelling," inasmuch as the Word of God
dwelt in the man, as in a temple; secondly, "by unity of intention,"
inasmuch as the will of the man was always in agreement with the will
of the Word of God; thirdly, "by operation," inasmuch as they said
the man was the instrument of the Word of God; fourthly, "by
greatness of honor," inasmuch as all honor shown to the Son of God
was equally shown to the Son of man, on account of His union with the
Son of God; fifthly, "by equivocation," i.e. communication of names,
inasmuch as we say that this man is God and the Son of God. Now it is
plain that these modes imply an accidental union.

But some more recent masters, thinking to avoid these heresies,
through ignorance fell into them. For some conceded one person in
Christ, but maintained two hypostases, or two supposita, saying that
a man, composed of body and soul, was from the beginning of his
conception assumed by the Word of God. And this is the first opinion
set down by the Master (Sent. iii, D, 6). But others desirous of
keeping the unity of person, held that the soul of Christ was not
united to the body, but that these two were mutually separate, and
were united to the Word accidentally, so that the number of persons
might not be increased. And this is the third opinion which the
Master sets down (Sent. iii, D, 6).

But both of these opinions fall into the heresy of Nestorius; the
first, indeed, because to maintain two hypostases or supposita in
Christ is the same as to maintain two persons, as was shown above (A.
3). And if stress is laid on the word "person," we must have in mind
that even Nestorius spoke of unity of person on account of the unity
of dignity and honor. Hence the fifth Council (Constantinople II,
coll. viii, can. 5) directs an anathema against such a one as holds
"one person in dignity, honor and adoration, as Theodore and
Nestorius fool