When looking at St. Thomas's treatment of chastity in the Summa Theologica, one becomes rather disappointed because he treats it simply as restraining lustful desires and without any theological development of its positive outcome, save for traditional methods of avoiding lust such as prayer, meditation, fasting and the like.

Of course, as the theologian or philosopher looks to other areas in his Summa, St. Thomas does have a doctrine about sex, but it tends to be piecemeal and presented in the light of negatives, that is, what occurs when someone does not have chastity.

For example, in his treatment of the daughters of lust, Thomas makes the case that it first undermines the virtue of prudence because it has a negative outcome on the mind:

There are four stages in the mind's process of doing something. First, the simple apprehension of an end as good, and here unchastity causes blindness of mind...Second, the deliberating about what should be done to attain an end, and this too is interfered with by unchastity... Added to this is a rashness prompted by failure to heed advice, as we have noticed. Third, the decision as to what should be done, and this also can be hindered by unchastity... Fourth, the executive command of reason, and here enters an inconstancy caused by unchasteness, as when a person having made up his mind about what ought to be done, is swept away by concupiscence from doing it.1

Thomas is showing us in reverse what would happen if chastity were not in place. On the other hand, if chastity were in place, then, when trying to decide a course of action, the mind would be clear so as to take in the wise counsel of others, think through causes and effects of a particular decision, make a decision and carry it out.

When it comes to the will, Aquinas observes the following in two parts:

First, the desire for the end, and here self-love enters, namely an inordinate desire for pleasure and, to cap it, hatred of God because he forbids it.2

We have to keep in mind that Aquinas is thinking of a full-blown vice of lust, not a sexual sin of weakness. Self-love is not looked upon as something always inordinate or unreasonable and this hatred of God does not necessarily mean an emotional reaction but a willful reaction. God simply is not important anymore when the vice is rampant.

Next, lust produces other problems:

...Second, the working of the appetite for the things which service the end, and here an undue attachment to the present world enters, and a will to enjoy its pleasures, capped by a despair about the next world, for a person sunk in carnal delights has no taste for spiritual joys. (Ibid.)

Where there is ''no taste for spiritual joys,'' the spirit of prayer, devotion and religious contemplation becomes very difficult and the vice of acedia enters into a person so that he begins to think that virtue is evil and vice is good (ST II-II 35, 1).

Where there is chastity, however, there is the possibility for a theological hope for the next world and delight in spiritual things, especially religious contemplation. The means for growing in chastity then become more than mere means, namely, they become secondary ends since they become the sources of spiritual joy by increasing charity, the source of spiritual joy.

Aquinas' Supplementum

It is when the reader becomes familiar with Thomas's teaching on marriage in the Supplementum, (a compilation of his earlier writings by his secretary, Blessed Reginald Piperno, perhaps other secretaries and perhaps other disciples, that he can discover more about the range of the virtue of chastity.

In the following sections, Thomas is speaking about marital chastity which is the ordinary virtue for married people. He knew the objections and their answers based upon a lively and robust understanding of marriage coupled with a realism about the sexual troubles that can be involved in marriage.

Vowed chastity, an evangelical counsel, is for the very few who are called to it. Yet when married chastity is understood correctly, then pre-marital chastity can be understood more positively as motivated more profoundly than a mere keeping of a commandment of Christ not to think lustfully of members of the same or opposite sex. This, paradoxically, also prepares one for vowed chastity or promised celibacy of the priesthood.

How Is the Marriage Act Not Sinful?

The Supplementum begins its treatment in question 41 and, for the sake of brevity, one needs to first look at article 3, where Thomas asks the question: Whether the marriage act is always sinful? He answers in the following way:

If we suppose the corporeal nature to be created by the good God, we cannot hold that those things which pertain to the preservation of the corporeal nature and to which nature inclines are universally evil; wherefore, since the inclination to beget an offspring whereby the specific nature is preserved is from nature, it is impossible to maintain that the act of begetting children is universally unlawful, so that it be impossible to find the mean of virtue therein; unless we suppose, as some are mad enough to assert, that corruptible things were created by an evil god... wherefore this is a most wicked heresy (ST, vol. 3).

We know from the two sed contra of the same article that Thomas taught that the context for having children is marriage.

The second objection to question 41 maintains that since the prophets were not ''touched'' by the Holy Spirit when engaged in marital intercourse, then something is wrong about it. To which, Thomas answers:

We are united to God by the habitus of grace and not by the act of contemplation and love. Therefore whatever severs the former of these unions is always a sin, but not always that which severs the latter, since a lawful occupation about lower things distracts the mind so that it is not for actual union with God; and this is especially the case in carnal intercourse wherein the mind is withheld by the intensity for pleasure. For this reason those who have to contemplate Divine things or handle sacred things are enjoined not to have do with their wives for that particular time; and it is in this sense that the Holy Spirit, as regards the actual revelation of hidden things, did not touch the hearts of the prophets at the time of the marriage act (Suppl. 41, 3 ad 2).

Throughout the other writings of Aquinas, he holds to the distinction between an actual and a virtual act of a virtue. For instance, it is one thing to directly engage oneself in the love of God and another to be motivated by the same love while the mind is preoccupied on doing something else.

By far, the most severe objection to the marital act being virtuous is found in the sixth objection:

Further, excess in the passions corrupts virtue. Now there is always excess of pleasure in the marriage act, so much so that it absorbs reason which is man's principal good, wherefore the philosopher says (Ethic. vii, 11) that ''in the act it is impossible to understand anything.'' Therefore the marriage act is always a sin (Ibid.).

In his reply, the Supplementum makes a very important distinction:

The excess of passions that corrupts virtue not only hinders the act of reason, but also destroys the order of reason. The intensity of pleasure in the marriage act does not do this, since, although at the moment man is not being directed, he was previously directed by his reason (Ibid.).

Here the distinction between the ''act'' and the ''ordering'' of reason is essential because what motivates an action does not necessarily have to be thought of or reflected upon during a virtuous action, such as giving glory to God or wanting a child for the glory of God. These consequences do not need to be immediately in mind but only virtually, much like consecrating bread and wine and the mind wanders about a particular friend who is dying.

Why Can the Marital Act be Meritorious?

When the Supplementum speaks about a marriage act being meritorious, it gives further light on the character of a chaste marital act. Before reading the reply to question 41a.4, the fifth objection is important to note:

Further, that which cannot be done without venial sin is never meritorious, for a man cannot both merit and demerit at the same time. Now there is always a venial sin in the marriage act, since even the first movement in such like pleasures is a venial sin. Therefore the aforesaid act cannot be meritorious.

The Supplementum begins its argument in the two sed contras: any act is meritorious if done from charity, and quotes Paul, saying ''let the Husband render the debt to his wife''; and since every act of virtue is meritorious when prompted by charity, rendering the debt is an act of justice. The reply gives further nuances:

Since no act proceeding from a deliberate will is indifferent..., the marriage act is always either sinful or meritorious in one who is in the state of grace. For if the motive for the marriage act be a virtue, whether of justice that they may render the debt, or of religion, that they may beget children for the worship of God, it is meritorious. But if the motive be lust, yet not excluding the marriage blessings, namely that he would by no means be willing to go to another woman, it is a venial sin, while if he exclude the marriage blessing, so as to be disposed to act in like manner with any woman, it is a mortal sin. And nature cannot move without being either directed by reason, and thus it will be an act of virtue, or not so directed, and then it will be an act of lust.

Someone who is simply inclined by the desire of pleasure alone and does not direct it to a good end, may be sinning venially, as long as his or her intention is not contrary to the goods of marriage. Any partner may be committing a mortal sin, however, if the act is done simply and exclusively from a love of pleasure as an end in itself as if the spouse were solely a ''pleasure machine.''

The first movements of sexual arousal mentioned in the fifth objection can be the occasion of virtue or vice depending on what a person does with these movements as is the case with any temptation against any virtue.

Of themselves, the first movements of any sin are called in many places in the Summa ''venial sins,'' but analogously so, not univocally because they do not yet engage the consent of the will but are in some sense disorderly due to original sin and frequently the residue of past personal sin. So they can be turned to virtue or sin by the intellect and will.

The Goods of Marriage as Motivators

In question 49, article 4, the Supplementum explains more what they mean by the goods of marriage. It begins with a very pertinent objection, which is the first one:

It would seem that the marriage act cannot be altogether entirely without sin by the aforesaid goods of marriage [Here understood as offspring, fidelity and sacrament]. For whoever allows himself to lose a greater good for the sake of a lesser good sins because he allows it inordinately. Now the good of reason which is prejudiced in the marriage act is greater than the three marriage goods. Therefore the aforesaid goods do not suffice to excuse marital intercourse.

Objection three offers another hurdle to overcome in order to appreciate marital chastity:

Further, wherever there is immoderate passion there is moral vice. Now the marriage goods cannot prevent the pleasure in that act from being immoderate. Therefore they cannot excuse it from being a sin.

The reply is a lesson in fundamental moral theology, the second half of which shows what a signified act is:

...Now a human act is said to be good in two ways. In one way by goodness of virtue, and thus an act derives its goodness from those things which place it in the mean. This is what ''fidelity'' and ''offspring'' do in the marriage act... In another way, by goodness of the ''sacrament,'' in which way an act is said to be not only good, but also holy, and the marriage act derives this goodness from indissolubility of the union, in respect of which it signifies union of Christ with the Church. Thus it is clear that the aforesaid goods suffice to render the marriage act innocent.

The answer to the first of objection is easily quashed by observing that ''generically better actions are sometimes interrupted for some less good act.'' It refers to an idea mentioned above that one can and does lay aside the act of contemplation for other actions or good deeds such as eating and sleeping. But the reply to the third objection is more poignant:

The excess of passion that amounts to a sin does not refer to the passion's quantitative intensity, but to its proportion to reason; wherefore it is only when a passion goes beyond the bounds of reason that it is reckoned to be immoderate. Now the pleasure attaching to the marriage act while it is more intense in point of quantity, does not go beyond the limits previously appoint by reason before the commencement of the act, although reason is unable to regulate those limits during the pleasure itself.

Major Effect of Lust Repeated

When speaking about the effects of original sin, the Supplementum clearly teaches that one effect, which is a punishment of original sin, is that the lower powers and members do not of themselves easily follow reason. This is a penalty originating from within not imposed from without. Yet it has led to the posing of article six of question forty-nine: can someone have marital intercourse with his wife and have the intention not of a marriage good but merely of pleasure? The issue revolves around the word, ''merely.'' The reply merits being quoted fully:

Some say that whenever pleasure is the chief motive for the marriage act it is a mortal sin; that when it is an indirect motive it is a venial sin and that when it spurns the pleasure altogether and is displeasing, it is wholly void of venial sin; so it would be a mortal sin to seek pleasure in this act, a venial sin to take the pleasure when offered, but that perfection requires one to detest it. But this cannot be so, since according to the Philosopher (Ethic. x, 3, 4) the same judgment applies to pleasure as to action, because pleasure in a good action is good, and in an evil action evil; wherefore, as the marriage act is not evil in itself, neither will it be always a mortal sin to seek pleasure therein. Consequently the right answer to this question is that if pleasure be sought in such a way beyond the integrity (honestum) of marriage, so that, to wit, it is not as a wife but as a woman that a man treats his wife, it is a mortal sin; wherefore such a man is said to be too ardent a lover of his wife, because his ardor carries him away from the goods of marriage. If, however, he seeks pleasure within the bounds of marriage, so that it would not be sought in another than his wife, it is a venial sin.

Here his reasoning argues brilliantly in favor of accepting pleasure in an authentic marital act, but if it is an act motivated exclusively or only for pleasure and at the same time against the goods of marriage, then such pleasure is not virtuous pleasure but ''wanton'' pleasure without any reference to the goods of marriage.

A husband or wife need not have an actual intention at the moment to give glory of God while engaged in the action of marital love so long as that motive is there habitually. Likewise, he does not have to have an actual intention to the precise goods of marriage, so long as they are already present in a virtual intention. Such is the idea behind the answer to the third objection.10

Conclusion. Teenagers do not simply grow in chastity or continence solely by overcoming sexual temptations. Thomas reminds us in several places that, ''The virtues are all connected with one another, not materially, but formally, namely by their life drawn from practical wisdom and charity....''11

This is why it is so important that praying, doing chores, loving and respecting one's parents and being faithful to homework co-exist in the home. Where these actions are banished in favor of watching videos, misusing computers, cell phoning and excessively ''hanging out'' with one's peers, then parents foolishly begin to believe that their children are nearly saints and cannot sin. The possibility of future fruitful and faithful marriages becomes problematic. TP

2 Ibid.

3 Thomas will abandon this Augustinian way of speaking in his later works, but here he used it:

Although he does not actually refer the pleasure to God, he does not place his will's last end therein; otherwise he would seek it anywhere indifferently. Hence it does not follow that he enjoys a creature (an Augustinian way of saying, ''making it an end in itself''); but he uses (again an Augustinian work of saying that he does not make it the end in itself) a creature actually for his own sake, and himself, habitually, though not actually, for God's sake (ST Supp. 49, 6 ad 3).

4 Cf. ST II-II 134, 1-4. The virtue of magnificence presupposes great wealth spent well for the common good.

Father Cole, O.P., is associate professor at the Dominican House of Studies in Washington, D.C., and is the author of The Hidden Enemies of the Priesthood (Alba House, 2007. $22.95 pb, 1-800-343-2522).