good.

Wherefore from the very fact that man coveted a spiritual good above
his measure, as stated in the foregoing Article, it follows that he
coveted God's likeness inordinately.

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