On the contrary, It is written: "Be you perfect as also your heavenly Father is perfect" (Matt. 5:48).
I answer that, As the Philosopher relates (Metaph. xii), some ancient philosophers, namely, the Pythagoreans and Leucippus, did not predicate "best" and "most perfect" of the first principle. The reason was that the ancient philosophers considered only a material principle; and a material principle is most imperfect. For since matter as such is merely potential, the first material principle must be simply potential, and thus most imperfect. Now God is the first principle, not material, but in the order of efficient cause, which must be most perfect. For just as matter, as such, is merely potential, an agent, as such, is in the state of actuality. Hence, the first active principle must needs be most actual, and therefore most perfect; for a thing is perfect in proportion to its state of actuality, because we call that perfect which lacks nothing of the mode of its perfection.
Reply Obj. 1: As Gregory says (Moral. v, 26,29): "Though our lips can only stammer, we yet chant the high things of God." For that which is not made is improperly called perfect. Nevertheless because created things are then called perfect, when from potentiality they are brought into actuality, this word "perfect" signifies whatever is not wanting in actuality, whether this be by way of perfection or not.
Reply Obj. 2: The material principle which with us is found to be imperfect, cannot be absolutely primal; but must be preceded by something perfect. For seed, though it be the principle of animal life reproduced through seed, has previous to it, the animal or plant from which is came. Because, previous to that which is potential, must be that which is actual; since a potential being can only be reduced into act by some being already actual.
Reply Obj. 3: Existence is the most perfect of all things, for it is compared to all things as that by which they are made actual; for nothing has actuality except so far as it exists. Hence existence is that which actuates all things, even their forms. Therefore it is not compared to other things as the receiver is to the received; but rather as the received to the receiver. When therefore I speak of the existence of man, or horse, or anything else, existence is considered a formal principle, and as something received; and not as that which exists. _______________________
SECOND ARTICLE [I, Q. 4, Art. 2]
Whether the Perfections of All Things Are in God?
Objection 1: It seems that the perfections of all things are not in God. For God is simple, as shown above (Q. 3, A. 7); whereas the perfections of things are many and diverse. Therefore the perfections of all things are not in God.
Obj. 2: Further, opposites cannot coexist. Now the perfections of things are opposed to each other, for each thing is perfected by its specific difference. But the differences by which genera are divided, and species constituted, are opposed to each other. Therefore because opposites cannot coexist in the same subject, it seems that the perfections of all things are not in God.
Obj. 3: Further, a living thing is more perfect than what merely exists; and an intelligent thing than what merely lives. Therefore life is more perfect than existence; and knowledge than life. But the essence of God is existence itself. Therefore He has not the perfections of life, and knowledge, and other similar perfections.