It must, however, be observed that the proper object of the appetite is a thing not possessed. Now spiritual good, in so far as the rational creature participates in the Divine likeness, may be considered in reference to three things. First, as to natural being: and this likeness was imprinted from the very outset of their creation, both on man—of whom it is written (Gen. 1:26) that God made man "to His image and likeness"—and on the angel, of whom it is written (Ezech. 28:12): "Thou wast the seal of resemblance." Secondly, as to knowledge: and this likeness was bestowed on the angel at his creation, wherefore immediately after the words just quoted, "Thou wast the seal of resemblance," we read: "Full of wisdom." But the first man, at his creation, had not yet received this likeness actually but only in potentiality. Thirdly, as to the power of operation: and neither angel nor man received this likeness actually at the very outset of his creation, because to each there remained something to be done whereby to obtain happiness.
Accordingly, while both (namely the devil and the first man) coveted God's likeness inordinately, neither of them sinned by coveting a likeness of nature. But the first man sinned chiefly by coveting God's likeness as regards "knowledge of good and evil," according to the serpent's instigation, namely that by his own natural power he might decide what was good, and what was evil for him to do; or again that he should of himself foreknow what good and what evil would befall him. Secondarily he sinned by coveting God's likeness as regards his own power of operation, namely that by his own natural power he might act so as to obtain happiness. Hence Augustine says (Gen. ad lit. xi, 30) that "the woman's mind was filled with love of her own power." On the other hand, the devil sinned by coveting God's likeness, as regards power. Wherefore Augustine says (De Vera Relig. 13) that "he wished to enjoy his own power rather than God's." Nevertheless both coveted somewhat to be equal to God, in so far as each wished to rely on himself in contempt of the order of the Divine rule.
Reply Obj. 1: This argument considers the likeness of nature: and man did not sin by coveting this, as stated.
Reply Obj. 2: It is not a sin to covet God's likeness as to knowledge, absolutely; but to covet this likeness inordinately, that is, above one's measure, this is a sin. Hence Augustine commenting on Ps. 70:18, "O God, who is like Thee?" says: "He who desires to be of himself, even as God is of no one, wishes wickedly to be like God. Thus did the devil, who was unwilling to be subject to Him, and man who refused to be, as a servant, bound by His command."
Reply Obj. 3: This argument considers the likeness of equality. _______________________
THIRD ARTICLE [II-II, Q. 163, Art. 7]
Whether the Sin of Our First Parents Was More Grievous Than Other Sins?
Objection 1: It would seem that the sin of our first parents was more grievous than other sins. For Augustine says (De Civ. Dei xiv, 15): "Great was the wickedness in sinning, when it was so easy to avoid sin." Now it was very easy for our first parents to avoid sin, because they had nothing within them urging them to sin. Therefore the sin of our first parents was more grievous than other sins.
Obj. 2: Further, punishment is proportionate to guilt. Now the sin of our first parents was most severely punished, since by it "death entered into this world," as the Apostle says (Rom. 5:12). Therefore that sin was more grievous than other sins.
Obj. 3: Further, the first in every genus is seemingly the greatest (Metaph. ii, 4 [*Ed. Diel. i, 1]). Now the sin of our first parents was the first among sins of men. Therefore it was the greatest.