I answer that, As the whole Church is termed one mystic body from its likeness to the natural body of a man, which in divers members has divers acts, as the Apostle teaches (Rm. 12; 1 Cor. 12), so likewise Christ is called the Head of the Church from a likeness with the human head, in which we may consider three things, viz. order, perfection, and power: "Order," indeed; for the head is the first part of man, beginning from the higher part; and hence it is that every principle is usually called a head according to Ezech. 16:25: "At every head of the way, thou hast set up a sign of thy prostitution"---"Perfection," inasmuch as in the head dwell all the senses, both interior and exterior, whereas in the other members there is only touch, and hence it is said (Is. 9:15): "The aged and honorable, he is the head"---"Power," because the power and movement of the other members, together with the direction of them in their acts, is from the head, by reason of the sensitive and motive power there ruling; hence the ruler is called the head of a people, according to 1 Kgs. 15:17: "When thou wast a little one in thy own eyes, wast thou not made the head of the tribes of Israel?" Now these three things belong spiritually to Christ. First, on account of His nearness to God His grace is the highest and first, though not in time, since all have received grace on account of His grace, according to Rm. 8:29: "For whom He foreknew, He also predestinated to be made conformable to the image of His Son; that He might be the first-born amongst many brethren." Secondly, He had perfection as regards the fulness of all graces, according to Jn. 1:14, "We saw Him [Vulg.: 'His glory'] . . . full of grace and truth," as was shown, Question [7], Article [9]. Thirdly, He has the power of bestowing grace on all the members of the Church, according to Jn. 1:16: "Of His fulness we have all received." And thus it is plain that Christ is fittingly called the Head of the Church.
