Assigned to Lust?

Objection 1: It would seem that six species are unfittingly assigned
to lust, namely, "simple fornication, adultery, incest, seduction,
rape, and the unnatural vice." For diversity of matter does not
diversify the species. Now the aforesaid division is made with regard
to diversity of matter, according as the woman with whom a man has
intercourse is married or a virgin, or of some other condition.
Therefore it seems that the species of lust are diversified in this
way.

Obj. 2: Further, seemingly the species of one vice are not
differentiated by things that belong to another vice. Now adultery
does not differ from simple fornication, save in the point of a man
having intercourse with one who is another's, so that he commits an
injustice. Therefore it seems that adultery should not be reckoned a
species of lust.

Obj. 3: Further, just as a man may happen to have intercourse with a
woman who is bound to another man by marriage, so may it happen that
a man has intercourse with a woman who is bound to God by vow.
Therefore sacrilege should be reckoned a species of lust, even as
adultery is.

Obj. 4: Further, a married man sins not only if he be with another
woman, but also if he use his own wife inordinately. But the latter
sin is comprised under lust. Therefore it should be reckoned among
the species thereof.

Obj. 5: Further, the Apostle says (2 Cor. 12:21): "Lest again, when I
come, God humble me among you, and I mourn many of them that sinned
before, and have not done penance for the uncleanness and fornication
and lasciviousness that they have committed." Therefore it seems that
also uncleanness and lasciviousness should be reckoned species of
lust, as well as fornication.

Obj. 6: Further, the thing divided is not to be reckoned among
its parts. But lust is reckoned together with the aforesaid: for it is
written (Gal. 5:19): "The works of the flesh are manifest, which are
fornication, uncleanness, immodesty, lust [Douay: 'luxury']."
Therefore it seems that fornication is unfittingly reckoned a species
of lust.

_On the contrary,_ The aforesaid division is given in the Decretals
36, qu. i [*Append. Grat. ad can. Lex illa].

_I answer that,_ As stated above (Q. 153, A. 3), the sin of lust
consists in seeking venereal pleasure not in accordance with right
reason. This may happen in two ways. First, in respect of the matter
wherein this pleasure is sought; secondly, when, whereas there is d