s from that which is
essential and not from that which is accidental: because what is
accidental is outside the specific nature. Consequently sins differ
specifically on the part of the voluntary acts rather than of the
inordinateness inherent to sin. Now voluntary acts differ in species
according to their objects, as was proved above (Q. 18, A. 2).
Therefore it follows that sins are properly distinguished in species
by their objects.

Reply Obj. 1: The aspect of good is found chiefly in the end: and
therefore the end stands in the relation of object to the act of the
will which is at the root of every sin. Consequently it amounts to
the same whether sins differ by their objects or by their ends.

Reply Obj. 2: Sin is not a pure privation but an act deprived of its
due order: hence sins differ specifically according to the objects of
their acts rather than according to their opposites, although, even
if they were distinguished in reference to their opposite virtues, it
would come to the same: since virtues differ specifically according
to their objects, as stated above (Q. 60, A. 5).

Reply Obj. 3: In various things, differing in species or genus,
nothing hinders our finding one formal aspect of the object, from
which aspect sin receives its species. It is thus that pride seeks
excellence in reference to various things; and avarice seeks
abundance of things adapted to human use.
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SECOND ARTICLE [I-II, Q. 72, Art. 2]

Whether Spiritual Sins Are Fittingly Distinguished from Carnal Sins?

Objection 1: It would seem that spiritual sins are unfittingly
distinguished from carnal sins. For the Apostle says (Gal. 5:19):
"The works of the flesh are manifest, which are fornication,
uncleanness, immodesty, luxury, idolatry, witchcrafts," etc. from
which it seems that all kinds of sins are works of the flesh. Now
carnal sins are called works of the flesh. Therefore carnal sins
should not be distinguished from spiritual sins.

Obj. 2: Further, whosoever sins, walks according to the flesh, as
stated in Rom. 8:13: "If you live according to the flesh, you shall
die. But if by the spirit you mortify the deeds of the flesh, you
shall live." Now to live or walk according to the flesh seems to
pertain to the nature of carnal sin. Therefore carnal sins should not
be distinguished from spiritual sins.

Obj. 3: Further, the higher part of the soul, which is the mind or
reason, is called the spirit, accordin