Objection 1. It would seem that the daughters of lust are unfittingly reckoned to be "blindness of mind, thoughtlessness, inconstancy, rashness, self-love, hatred of God, love of this world and abhorrence or despair of a future world." For mental blindness, thoughtlessness and rashness pertain to imprudence, which is to be found in every sin, even as prudence is in every virtue. Therefore they should not be reckoned especially as daughters of lust.
Objection 2. Further, constancy is reckoned a part of fortitude, as stated above (128, ad 6; 137, 3). But lust is contrary, not to fortitude but to temperance. Therefore inconstancy is not a daughter of lust.
Objection 3. Further, "Self-love extending to the contempt of God" is the origin of every sin, as Augustine says (De Civ. Dei xiv, 28). Therefore it should not be accounted a daughter of lust.
Objection 4. Further, Isidore [QQ. in Deut., qu. xvi] mentions four, namely, "obscene," "scurrilous," "wanton" and "foolish talking." There the aforesaid enumeration would seem to be superfluous.
On the contrary, stands the authority of Gregory (Moral. xxxi, 45).
I answer that, When the lower powers are strongly moved towards their objects, the result is that the higher powers are hindered and disordered in their acts. Now the effect of the vice of lust is that the lower appetite, namely the concupiscible, is most vehemently intent on its object, to wit, the object of pleasure, on account of the vehemence of the pleasure. Consequently the higher powers, namely the reason and the will, are most grievously disordered by lust.
Now the reason has four acts in matters of action. First there is simple understanding, which apprehends some end as good, and this act is hindered by lust, according to Daniel 13:56, "Beauty hath deceived thee, and lust hath perverted thy heart." On this respect we have "blindness of mind." The second act is counsel about what is to be done for the sake of the end: and this is also hindered by the concupiscence of lust. Hence Terence says (Eunuch., act 1, sc. 1), speaking of lecherous love: "This thing admits of neither counsel nor moderation, thou canst not control it by counseling." On this respect there is "rashness," which denotes absence of counsel, as stated above (Question 53, Article 3). The third act is judgment about the things to be done, and this again is hindered by lust. For it is said of the lustful old men (Daniel 13:9): "They perverted their own mind... that they might not... remember just judgments." On this respect there is "thoughtlessness." The fourth act is the reason's command about the thing to be done, and this also is impeded by lust, in so far as through being carried away by concupiscence, a man is hindered from doing what his reason ordered to be done. [To this "inconstancy" must be referred.] [The sentence in brackets is omitted in the Leonine edition.] Hence Terence says (Eunuch., act 1, sc. 1) of a man who declared that he would leave his mistress: "One little false tear will undo those words."
On the part of the will there results a twofold inordinate act. One is the desire for the end, to which we refer "self-love," which regards the pleasure which a man desires inordinately, while on the other hand there is "hatred of God," by reason of His forbidding the desired pleasure. The other act is the desire for the things directed to the end. With regard to this there is "love of this world," whose pleasures a man desires to enjoy, while on the other hand there is "despair of a future world," because through being held back by carnal pleasures he cares not to obtain spiritual pleasures, since they are distasteful to him.
Reply to Objection 1. According to the Philosopher (Ethic. vi, 5), intemperance is the chief corruptive of prudence: wherefore the vices opposed to prudence arise chiefly from lust, which is the principal species of intemperance.
Reply to Objection 2. The constancy which is a part of fortitude regards hardships and objects of fear; but constancy in refraining from pleasures pertains to continence which is a part of temperance, as stated above (143). Hence the inconstancy which is opposed thereto is to be reckoned a daughter of lust. Nevertheless even the first named inconstancy arises from lust, inasmuch as the latter enfeebles a man's heart and renders it effeminate, according to Hosea 4:11, "Fornication and wine and drunkenness take away the heart [Douay: 'understanding']." Vegetius, too, says (De Re Milit. iii) that "the less a man knows of the pleasures of life, the less he fears death." Nor is there any need, as we have repeatedly stated, for the daughters of a capital vice to agree with it in matter (cf. 35, 4, ad 2; 118, 8, ad 1; 148, 6).
Reply to Objection 3. Self-love in respect of any goods that a man desires for himself is the common origin of all sins; but in the special point of desiring carnal pleasures for oneself, it is reckoned a daughter of lust.
Reply to Objection 4. The sins mentioned by Isidore are inordinate external acts, pertaining in the main to speech; wherein there is a fourfold inordinateness. First, on account of the matter, and to this we refer "obscene words": for since "out of the abundance of the heart the mouth speaketh" (Matthew 12:34), the lustful man, whose heart is full of lewd concupiscences, readily breaks out into lewd words. Secondly, on account of the cause: for, since lust causes thoughtlessness and rashness, the result is that it makes a man speak without weighing or giving a thought to his words. which are described as "scurrilous." Thirdly, on account of the end: for since the lustful man seeks pleasure, he directs his speech thereto, and so gives utterance to "wanton words." Fourthly, on account of the sentiments expressed by his words, for through causing blindness of mind, lust perverts a man's sentiments, and so he gives way "to foolish talking," for instance, by expressing a preference for the pleasures he desires to anything else.
Source: Summa Theologica (New Advent)