Reply Obj. 1: Christ's influence over men is chiefly with regard to their souls; wherein men agree with angels in generic nature, though not in specific nature. By reason of this agreement Christ can be said to be the Head of the angels, although the agreement falls short as regards the body.
Reply Obj. 2: The Church, on earth, is the congregation of the faithful; but, in heaven, it is the congregation of comprehensors. Now Christ was not merely a wayfarer, but a comprehensor. And therefore He is the Head not merely of the faithful, but of comprehensors, as having grace and glory most fully.
Reply Obj. 3: Augustine here uses the similitude of cause and effect, i.e. inasmuch as corporeal things act on bodies, and spiritual things on spiritual things. Nevertheless, the humanity of Christ, by virtue of the spiritual nature, i.e. the Divine, can cause something not only in the spirits of men, but also in the spirits of angels, on account of its most close conjunction with God, i.e. by personal union. _______________________
FIFTH ARTICLE [III, Q. 8, Art. 5]
Whether the Grace of Christ, As Head of the Church, Is the Same As
His Habitual Grace, Inasmuch As He Is Man?
Objection 1: It would seem that the grace whereby Christ is Head of the Church and the individual grace of the Man are not the same. For the Apostle says (Rom. 5:15): "If by the offense of one many died, much more the grace of God and the gift, by the grace of one man, Jesus Christ, hath abounded unto many." But the actual sin of Adam is distinct from original sin which he transmitted to his posterity. Hence the personal grace which is proper to Christ is distinct from His grace, inasmuch as He is the Head of the Church, which flows to others from Him.
Obj. 2: Further, habits are distinguished by acts. But the personal grace of Christ is ordained to one act, viz. the sanctification of His soul; and the capital grace is ordained to another, viz. to sanctifying others. Therefore the personal grace of Christ is distinct from His grace as He is the Head of the Church.
Obj. 3: Further, as was said above (Q. 6, A. 6), in Christ we distinguish a threefold grace, viz. the grace of union, capital grace, and the individual grace of the Man. Now the individual grace of Christ is distinct from the grace of union. Therefore it is also distinct from the capital grace.
On the contrary, It is written (John 1:16): "Of His fulness we all have received." Now He is our Head, inasmuch as we receive from Him. Therefore He is our Head, inasmuch as He has the fulness of grace. Now He had the fulness of grace, inasmuch as personal grace was in Him in its perfection, as was said above (Q. 7, A. 9). Hence His capital and personal grace are not distinct.
I answer that, Since everything acts inasmuch as it is a being in act, it must be the same act whereby it is in act and whereby it acts, as it is the same heat whereby fire is hot and whereby it heats. Yet not every act whereby anything is in act suffices for its being the principle of acting upon others. For since the agent is nobler than the patient, as Augustine says (Gen. ad lit. xii, 16) and the Philosopher (De Anima iii, 19), the agent must act on others by reason of a certain pre-eminence. Now it was said above (A. 1; Q. 7, A. 9) grace was received by the soul of Christ in the highest way; and therefore from this pre-eminence of grace which He received, it is from Him that this grace is bestowed on others—and this belongs to the nature of head. Hence the personal grace, whereby the soul of Christ is justified, is essentially the same as His grace, as He is the Head of the Church, and justifies others; but there is a distinction of reason between them.