n this way it is true, for whatever subsists in human nature is
a person. Secondly it may be taken that in Christ a proper
personality, caused by the principles of the human nature, is due to
the human nature; and in this way Christ as Man is not a person,
since the human nature does not exist of itself apart from the Divine
Nature, and yet the notion of person requires this.

Reply Obj. 1: It belongs to every man to be a person, inasmuch as
everything subsisting in human nature is a person. Now this is proper
to the Man Christ that the Person subsisting in His human nature is
not caused by the principles of the human nature, but is eternal.
Hence in one way He is a person, as Man; and in another way He is
not, as stated above.

Reply Obj. 2: The "individual substance," which is included in the
definition of a person, implies a complete substance subsisting of
itself and separate from all else; otherwise, a man's hand might be
called a person, since it is an individual substance; nevertheless,
because it is an individual substance existing in something else, it
cannot be called a person; nor, for the same reason, can the human
nature in Christ, although it may be called something individual and
singular.

Reply Obj. 3: As a person signifies something complete and
self-subsisting in rational nature, so a hypostasis, suppositum, and
being of nature in the genus of substance, signify something that
subsists of itself. Hence, as human nature is not of itself a person
apart from the Person of the Son of God, so likewise it is not of
itself a hypostasis or suppositum or a being of nature. Hence in the
sense in which we deny that "Christ as Man is a person" we must deny
all the other propositions.
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QUESTION 17

OF CHRIST'S UNITY OF BEING
(In Two Articles)

We must now consider what pertains to Christ's unity in common. For,
in their proper place, we must consider what pertains to unity and
plurality in detail: thus we concluded (Q. 9) that there is not only
one knowledge in Christ, and it will be concluded hereafter (Q. 35,
A. 2) that there is not only one nativity in Christ.

Hence we must consider Christ's unity (1) of being; (2) of will;
(3) of operation.

Under the first head there are two points of inquiry:

(1) Whether Christ is one or two?

(2) Whether there is only one being in Christ?
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FIRST ARTICLE [III, Q. 17, Art. 1]

Whether Christ Is One or Two?