1. Pastoral treatment of quasi-compulsive sinners through weakness has become increasingly mild in this century. This development long antedated Vatican II. Faithful theologians began to suggest that perhaps under certain conditions quasi-compulsive sins of weakness might not be mortal sins. This seemed a plausible view inasmuch as the quasi-compulsive sinner goes on fighting the good fight, is anguished by failures, and often shows other signs of a real and serious Christian commitment. In recent years, even many bishops who affirm received Catholic teaching on matters such as contraception have urged pastoral approaches which seem reasonable only if it is supposed that quasi-compulsive sins of weakness need not be mortal sins despite meeting all three conditions for mortal sin. This sort of view also underlies much thinking about fundamental option (criticized in 16‑E).
2. However, the pastoral practice formed by classical moral theology during a period of several centuries uniformly treated sins of weakness in grave matter as mortal. It does not seem possible to admit an implicit error in the pastoral practice of the whole Church which bound the consciences of the faithful under pain of mortal sin. Such practice teaches implicitly, and this binding and universal moral teaching meets the conditions for the infallibility of the ordinary magisterium (which will be explained in 35‑D).
St. Paul confronts the problem of weakness experienced by Christians after their baptism. He recognizes the ambivalence of the condition of the Christian who must still struggle to overcome weakness. But he makes no concession to the possible view that sins of weakness might not be mortal provided one struggles against them. Rather, his emphasis is upon the real possibility of avoiding evil, a possibility which comes not from oneself but from the power of the Spirit (see Rom 6.12–8.17).5
Similarly, the writer of Hebrews emphasizes that our Lord is a compassionate high priest who can sympathize with our weakness. But this emphasis is to stress the sympathy he has because he himself was tempted, and so will be prompt to help us when we are tempted. The point is that sin can be avoided. Hebrews contains exhortations to people who might sin through weakness; if they do, the sin is considered most serious (see Heb 2.14–18; 4.15–16; 6.4–8).
3. Moreover, in treating the question of certain sins of weakness, recent documents of the magisterium implicitly assume that, as long as there is a free choice—together, of course, with sufficient reflection and grave matter—there is mortal sin. They also state that responsibility ought to be presumed.
4. For example, in its Declaration on Certain Questions Concerning Sexual Ethics, the Sacred Congregation for the Doctrine of the Faith says of a typical case of quasi-compulsive sin of weakness: “On the subject of masturbation modern psychology provides much valid and useful information for formulating a more equitable judgment on moral responsibility and for orienting pastoral action. Psychology helps one to see how the immaturity of adolescence (which can sometimes persist after that age), psychological imbalance or habit can influence behavior, diminishing the deliberate character of the act and bringing about a situation whereby subjectively there may not always be serious fault. But in general, the absence of serious responsibility must not be presumed; this would be to misunderstand people’s moral capacity.”6
5. The same position is developed at greater length in the teaching of Pius XII on the formation of Christian consciences in young people. His discourse on this subject acquired special importance because Vatican II incorporated it by reference and so made it part of its own teaching concerning the responsibility of Catholics to form their consciences in accord with the teaching of the Church (see DH 14; GS 16).
Pius XII, in a discourse on the correct formation of the Christian consciences of young people, rejects various false principles and draws the following relevant conclusions:
Therefore, being conscious of the right and of the duty of the Apostolic See to intervene authoritatively, when necessary, on moral questions, We declare to educators and to youth: the divine commandment to be pure in soul and body applies without diminution also to today’s youth. The youth of today has also the moral obligation and the possibility of keeping itself pure with the aid of grace. We reject, therefore, as erroneous the claim of those who consider inevitable the failings of the age of puberty, considered by them of no great import and almost as if they were not a grave fault, because, they add, passion cancels the liberty which is required to make a person morally responsible for an act.
On the contrary, it is required from a wise educator that, without neglecting to impress on his youthful charges the noble qualities of purity so as to induce them to love and desire it for its own sake, he should at the same time clearly inculcate the commandment as it stands, in all its gravity and earnestness as a divine order. He will thus urge them to avoid immediate occasions, he will comfort them in the struggle, of which he shall not hide the hardness, he will induce them to embrace courageously the sacrifice demanded by virtue, and he will exhort them to persevere and not to fall into the danger of surrendering from the very beginning and thus succumbing passively to perverse habits.7
6. There can of course be a lack of sufficient reflection or of free choice in particular cases. The Sacred Congregation mentions immaturity of adolescence (which can persist), psychological imbalance, and habit. The possible effect of immaturity was explained (in A and D): Some individuals in respect to some matters lack sufficient maturity of conscience to grasp in a minimally adequate way the moral truth concerning the gravity of what they choose. Psychological imbalance and habit can lead an individual to act without choosing (so that the behavior is not a morally significant act) or to choose only after losing sight of the gravity of the matter (so that the actual choice is only a venial sin).
7. If, however, one does assent to the judgment that a certain matter is grave and simultaneously chooses to do it, then one commits a mortal sin, even though the choice is made reluctantly, is motivated by passion, and is conditioned by the intention of repenting soon after.
8. The following consideration shows why this is so. Mortal sin is a self-disposition incompatible with love of God, because (for the Christian) contrary to the fundamental commitment of faith (see 16‑G). When, however, a Christian is aware—truly aware, at the level of moral truth—that a choice concerns grave matter, he or she is also aware that this choice cannot be made without being unfaithful, that is, without acting against the claims of faith. One knows that in making such a choice, one will surrender the protection of one’s upright fundamental option. If one then gives in to temptation, the sinful choice is a self-determination at odds with the commitment of faith and so incompatible with the love of God by which one should respond in faith to him.
9. Thus, whenever the usual conditions are really fulfilled, mortal sin is committed. By definition, these conditions are fulfilled, assuming grave matter, in all sins of weakness of the third and fourth kinds: isolated sins of weakness inconsistent with previous upright character and quasi-compulsive sins of weakness. Despite the mitigation of guilt, all such sins of weakness are mortal sins.
10. To deny this is at least implicitly to deny something of the reality of free choice and moral responsibility. One would have to suppose that in making choices people do not do what they are willing to do but something else which they cannot even know. This line of thinking points back to the mysteries of the indefensible theories of fundamental option (criticized in 16‑D and 16‑E).
11. The recent documents of the magisterium cited above also make it clear that those who appear to be quasi-compulsive sinners in grave matter must generally be presumed really to be sinning mortally. It is hard to see how one could have reasonable grounds for setting aside this presumption if the conditions which define “quasi-compulsive sin of weakness” seem to be met, for in any such case the individual seems to have minimally sufficient understanding of the gravity of the matter and also thinks he or she gave in to the temptation despite this awareness.
12. Normally, then, both confessor and sinner should suppose that apparent quasi-compulsive sins of weakness in grave matter really are mortal sins. All mortal sins must be confessed and so, therefore, must these. If one truly doubts whether one has made a sinful choice, one is not obliged to confess it. But usually this is not the case with quasi-compulsive sinners, who know that at a certain point they gave in to temptation.
A particular penitent who also accepts probabilism and who sincerely regards as solidly probable a milder theological opinion concerning the presumption of grave guilt in cases of apparent quasi-compulsive sin of weakness need not be considered in bad faith and must not be refused absolution if he or she continues in other respects to resist the temptation and avoid serious sin. However, anyone who understands what has been explained in this question, who is wholly faithful to the Church’s teaching, and who understands what was explained about probabilism (in 12‑D) will realize that apparent quasi-compulsive sins of weakness usually must be presumed to be mortal sins and should be confessed as such.
13. Although one may doubt whether one has committed a mortal sin, one does well to confess anything one suspects is a mortal sin. This is particularly true of a quasi-compulsive sinner, for once such a person adopts the view that seeming mortal sins might not be such and need not be confessed, he or she may well stop attempting to refrain from such actions. But then, the sins no longer will be sins of weakness and will certainly be mortal.
14. A good confession demands sincere contrition, which includes a real purpose of amendment. Contrition should not be considered insincere simply because, in sinning, the person also consciously intended to repent later. Rather, what is at issue as far as sincerity is concerned is whether the sinner really wills to avoid and reject the sin, to live in the future in unbroken faithfulness. And this is shown by readiness to make a real effort to deal with the occasions of sin.
15. Similarly, purpose of amendment is not a matter of speculation. One must simply decide to stop sinning. To decide this, one must believe it possible. Future sin must not be accepted as likely, for this would be to suppose that grace is insufficient or sin not a matter of free choice. Still a discouraged individual may not be able to help feeling that future sin is likely, while nevertheless having a genuine purpose of amendment. This, once more, is shown by readiness to do what is possible to deal with the occasions of sin.
Even if there is some grasp upon moral truth, the mentality of apparent quasi-compulsive sinners through weakness at least involves inadequately integrated elements of superego and social convention. These are essential underlying assumptions in the proposition: I can sin now and repent shortly. This state of mind is not one of presumption contrary to the virtue of hope; as St. Thomas already pointed out, it is characteristic of sin of weakness and mitigates it (see S.t., 2–2, q. 21, a. 2, ad 3).
However, to sin with an intention to repent is to gamble, and to gamble with right and wrong is to suppose that evil is a naughty deed one can repair by accepting one’s spanking, or a breaking of rules one can make good by following relevant rules. Quasi-compulsive sinners through weakness must learn what mortal sin really is. Then they will see how inappropriate are their attitudes toward it. This growth in insight will open the way to instruction about the larger realities of Christian life: To overcome sin one must pursue holiness; to pursue holiness one must discern one’s personal vocation and commit oneself to it.
This growth in insight also is necessary if the sinner through weakness is to clarify his or her own mind concerning the sinful acts. It is important to understand the intrinsic point of the Christian norm, and the inherent meaning of its sinful violation. Moreover, most people have only a vague notion of what the conditions for mortal sin mean, and instruction on this score probably will not be grasped until it becomes personally relevant. However, when a person of sufficient age and intelligence realizes the need for it, he or she can come to understand what it means to reflect sufficiently and consent fully. In learning this, one learns more clearly what freedom and moral responsibility are.
5. See F. Prat, La Théologie de Saint Paul, 43 ed. (Paris: Beauchesne, 1961), 1:268–84; 2:81–90; Lucien Cerfaux, The Christian in the Theology of St. Paul (New York: Herder and Herder, 1967), 446–66.
6. Sacred Congregation for the Doctrine of the Faith, Declaration on Certain Questions Concerning Sexual Ethics (Washington, D.C.: United States Catholic Conference, 1976), 10 (68 AAS  87). Anyone who claims that the Congregation in this document has departed in any significant way from received Catholic positions (in particular, the teaching of Pius XII on the presumption which must be made in cases of sin of weakness) will find a conciliatory interpretation blocked by the criticisms dissenting theologians leveled against the document shortly after its publication. For a summary of some of these, see Richard A. McCormick, S.J., Notes on Moral Theology: 1965–1980 (Washington, D.C.: University Press of America, 1981), 674–78.
7. Pius XII, “De Conscientia Christiana in Iuvenibus Recte Efformanda,” 44 AAS (1952) 275–76; The Pope Speaks: The Teaching of Pope Pius XII, ed. Michael Chinigo (New York: Pantheon Books, 1957), 97. Outside the quoted passage, this translation omits some paragraphs, which only add force to the message.