Aquinas on Mortal Sins of Passion

Though Aquinas clearly affirms that the influence of passions on the will can decrease the degree of voluntariness, and thus the merit or demerit of good actions or sins, when it comes to gravely disordered acts, such as fornication, masturbation, or theft, he still sees the issue as basically black or white: either the act is voluntary, and then it is a mortal sin; or it is not voluntary, and then it is not properly a sin at all. He affirms this position both in the De Malo, and in the Summa Theologiae.

De Malo, question 3, article 10

Whether sins committed out of passion are imputed to man as mortal fault

It should be said that since men sometimes commit adultery out of weakness or passion, and do many crimes or shameful things, as Peter did when he denied Christ out of fear, no one should have any doubt that sins perpetrated out of passion are sometimes mortal.

To understand this we should consider that the necessity based on something one's will has power over does not keep an act from being a mortal sin, just as, if someone stabs a dagger in someone's vital members it is necessary that that man die, but stabbing him is voluntary. Hence the death of the man who is stabbed is imputed to the one who struck him as a mortal fault.

And it is similar in the case we are considering; for given that reason is bound by passion, it is necessary that a disordered choice follow, but the will has the power to repel this bond of reason. For it was said that reason is bound due to the soul's intention being vehemently drawn to the act of the sensitive appetite; hence it is turned away from considering in particular that which it knows universally. But the will has the power to turn the intention to something or not. Hence it has the power to keep reason from being bound. Therefore the act committed on account of reason's being bound is voluntary; hence it is not excused from fault, even mortal fault. But if the bond of reason by passion goes so far that it is not in the will's power to remove such a bond, as if someone becomes insane through some passion of the soul, whatever he commits would not be imputed to him as fault, as neither would it be imputed to any insane person—unless perhaps such a passion was voluntary from its very beginning; for then the will could from the beginning prevent the passion for going so far; thus murder committed through drunkenness is imputed to man as fault, since the beginning of drunkenness was voluntary.

Summa Theologiae I-II, Question 77, Article 8

Whether a sin committed out of passion can be mortal

It should be said that mortal sin, as was said above, consists in turning away from the last end, which is God; this turning away pertains to the reason in its deliberation, since it is reason that orders things to the end. Therefore the only way in which the soul's inclination to something which is contrary to the last end can be not a mortal sin, is because reason is unable to resist this inclination by its deliberation, as is the case in sudden movements of the passions. But when someone out of passion goes on to do a sinful act, or to deliberate consent, this does not happen suddenly. Hence reason by deliberating can resist this further act; for it can get rid of, or at least prevent it [from leading to action], as was said above. Hence if it does not resist it, it is a mortal sin. Thus we see that many murders and adulteries are committed out of passion.

In response to the third objection, which argues that mortal sin consists in turning away from God, and only man's spiritual faculty of reason can do this, while passion cannot strictly speaking turn toward or away from God, Aquinas argues:

It should be said that passion does not always impede reason totally from its act; hence it retains free judgment, so that it can turn away from or toward God. If, however, the use of reason were totally taken away, there would be neither a mortal nor a venial sin.

This response of Aquinas seems to indicate that his position is in fact quite a bit stronger than that "sin committed out of passion can be mortal"–that in his mind, every act that is objectively gravely disordered, if it is at all voluntary, though committed under the influence of passion, is a mortal sin.

Mortal Sin and Fundamental Option 2

In the previous post I attempted to describe a man who, as far as morally possible, related to his family in a manner analogous to the manner a Christian relates to God, so that even things that normally are not incompatible with marital love would exclude it.

We could also consider a more realistic case, in which a man's fight with his wife isn't incompatible with loving for her. There are, still, individual acts that are quite incompatible with love for her, e.g., attempting to kill one of their children, or signing over all his property to another woman for whom he has strong feelings. In this case, too, it's psychologically not possible for him to go rapidly back and forth from loving her to performing such acts incompatible with loving her, unless those acts are not really voluntary—and are performed only due to being drunk, for instance. Such acts that involve breaking off his love for his wife in most cases only complete and manifest a process begun long ago, of failing in love for her.

Aquinas on the Sin of Drunkenness

From the De Malo to the Summa Theologiae Aquinas apparently makes a shift in his judgment about drunkenness. While in the De Malo he says that getting drunk is of itself a venial sin, in the Summa Theologiae and in the Commentary on Romans (as well as the Commentary on 1 Corinthians), which are widely considered to be of a later date than the De Malo, he says that getting drunk is of itself a mortal sin.

De Malo

In the De Malo, q.2, a. 8, Aquinas asks whether a circumstance can make a venial sin into a mortal sin. The third objection argues that getting drunk once is a venial sin, while getting drunk many times is a mortal sin. Hence a circumstance (the frequency) makes a venial sin into a mortal one. He replies:

To the third it should be said that getting drunk many times is not a circumstance that constitutes a species of sin, and therefore as getting drunk once is a venial sin, so getting drunk many times is a venial sin, speaking per se; but accidentally and by way of disposition getting drunk many times can be a mortal sin, as for example, when by the custom of drinking someone comes to have so great complacency in drunkenness that he would be willing to get drunk even if it involved the contempt of a divine precept. (De Malo, q.2, a. 8 )

Again in q. 7, a. 4, where the same question comes up again, a similar objection is raised:

1. Augustine says in a sermon on Purgatory that if anger is held onto for a long time, and if drunkenness is a regular (assidua) occurence, they are then numbered among mortal sins. But such sins are generically venial sins–otherwise they would always be mortal sins. Therefore a venial sin becomes mortal through the circumstance of regularity or duration. (De Malo, q. 7, a. 4)

He makes a similar reply, though with a different argument.

It should be said about drunkenness, that it in itself makes the reason actually not turned toward God, i.e., so long as the drunkenness lasts the reason cannot be turned toward God. And since a man is not obliged at all times to actually turn his reason towards God, drunkenness is not always a mortal sin; but when a man gets drunk regularly, it seems that he is not concerned about whether his reason is turned toward God, and in such a case drunkenness is a mortal sin, for it seems that on account of the pleasure of wine he despises the turning of his reason toward God. (De Malo, q. 7, a. 4, ad 1)

Summa Theologiae

In I-II, q. 88, a. 5, he asks whether some circumstance of an act can make a venial sin into a mortal sin. The first objection is of particular interest, because it is almost exactly the same as that in De Malo, q. 7, a. 4. Aquinas writes:

Augustine says in a sermon on Purgatory that if anger is held onto for a long time, and if drunkenness is a regular (assidua) occurence, they are then numbered among mortal sins. But anger and drunkenness are not generically mortal sins, but venial sins–otherwise they would always be mortal sins. Therefore a circumstance makes a venial sin into a mortal sin. (I-II, q. 88, a. 5)

In reply, he says:

About drunkenness we should say that that it has in itself the character of a mortal sin; for when a man without necessity and merely for the sake of the pleasure in wine, make himself unable to use his reason, by which a man is directed to God and avoids committing many sins, such an act is expressly contrary to virtue. But it can be a venial sin on account of some sort of ignorance or weakness, as when a man is ignorant of the strength of the wine, or of his own incapacity (for drinking), so that he does not expect to get drunk; for in such a case the drunkenness is not imputed to him as a sin, but only the excessive drinking. If, however, he gets drunk frequently, this ignorance can no longer excuse him, and his will seems to choose drunkenness rather than refraining from an excess of wine; hence the sin becomes again what it is by its own nature [namely a mortal sin]. (I-II, q. 88, a. 5, ad 1)

Again in the Secunda Secundae, q. 150, a. 2, where he takes up drunkenness specifically, and asks whether it is a mortal sin, he gives the same reply:

Someone may be well aware that he is drinking immoderately and thereby getting drunk, and yet he would rather be drunk than abstain from drink. Such a man is the one who is properly speaking called a drunkard [in contrast to persons who drink too much without knowing it, or get drunk without expecting it], because moral character comes not from things that occur accidentally and aside from the intention, but from that which is directly intended. In this way drunkenness is a mortal sin, because then a man willingly and knowingly deprives himself of the use of reason, bu which he performs virtuous deeds and avoids sin, and thus he sins mortally by running the risk of committing  sin. For Ambrose says in the book On the Patriarchs: "We say that one should avoid drunkenness, since it keeps us from avoiding grievous sins. For the things we avoid when sober, we unknowingly commit through drunkenness." Therefore drunkenness, speaking per se, is a mortal sin. (Secunda Secundae, q. 150, a. 2)

In the reply to the first objection he interprets Augustine's saying in the same way as he does in the Prima Secundae.

His treatment in his Commentary on Romans and on 1 Corinthians is very much like that in the Summa Theologiae.

How to Account for the Difference?

The divergence between the account in the De Malo and in the later writings could be explained in several ways:

(1) Aquinas may have become stricter in general, and thus stricter in his judgment of drunkenness. (This would be an interesting subject of research. I don't know of any studies investigating such a line of thought).

(1b) He may have gained more experience of the harmful things people do when drunk, and pronounces judgment accordingly.

(2) He may be envisioning quite different contexts. In the De Malo he may be envisioning, e.g., a monk in his cell who gets drunk by drinking too much wine, and the principal or only harmful consequence is that he can't pray or contemplate at that time, while in the other works he is envisioning a person engaged in various activities and in active relationships with other persons, who is liable to damage things or injure other persons if he is drunk.

Mortal Sin and Fundamental Option

One of the reasons why many theologians have been attracted to the theory of a "fundamental option" is that it seems in certain respects to correspond better to real-life experience. If we consider visible human relationships, between two married persons for example,we don't find persons who go frequently back and forth from being totally committed to each other, to selfishly rejecting each other, back to total commitment, and so on. As a rule, the relationship will overall either be gradually improving or deteriorating, and individual quarrels don't completely disrupt the relationship. If a man ceases to love his wife on account of a single dispute or fight, that would be taken as a sign he didn't really love her in the first place, or that he had been neglecting his love for her, letting various selfish interests break it down, and that the quarrel is only the terminus of a long process.

Leaving aside the theological aspect, based on God's covenant with man, the supernatural virtue of charity, etc., what is happening when a person resolves to live a certain manner of life, and yet occasionally, or perhaps frequently, performs concrete acts that are inconsistent with that? For example, he resolves to live for his family, and looks for his happiness within his family (and in the wider sense, within his society). But he sometimes performs acts, such as staying out excessively late drinking with his fellow workers, that don't make sense within that framework, but only make sense on the supposition of a preference for something else above happiness as a member of his family, within a framework in which what he wants is the ultimate point of reference, where self-love is the final measure. Or in other words, in terms of the end/means relationship, certain acts he does objectively can't be truly ordered towards the end of family happiness as a final goal, but only towards some other end, that may be thought of more vaguely (living a pleasant life), but that at any rate is some other final goal.

One might explain the situation in several ways:

1. The ultimate goal of his life is, and remains, the common good of his family and his happiness within that family, though he performs individual acts that don't make sense and are unreasonable in terms of that goal.

2. The ultimate goal of his life is all along some vague goal (living a good life, a social and pleasant life, or the like), in which his family's good is one element among others, though an important one.

3. The ultimate goal of his life is the good of his family most of the time, but when he does acts objectively contrary to that goal, then when he is doing those acts, he thereby re-orientates himself towards another final end, and remains directed towards that end until he makes a fresh resolve to live his life as a whole for his family.

The first and second explanations do seem, on the face of it, more plausible interpretations of what is going on than the third.

If we accept the first explanation, what would that mean in terms of the voluntariness of the man's acts? Since whatever one wills, one wills for the sake of one's final end, the man is therefore willing, for the sake of his final end, to do something actually inconsistent with that final end. This would seem to imply that his act is not perfectly voluntary, at least not in the respect in which it is contrary to his ultimate end. (This distinction, though it is often forgotten or overlooked, is an important one. An act may be completely voluntary in the sense that it is the result of a very conscious and explicit choice, without all of the goodness or badness of that act necessarily being voluntary).

The analogy one might make with love for God and the performance of sinful acts is, I think, clear. For the time we will continue to leave aside the issues pertaining to charity as an virtue infused by God and dependent on grace. A person who resolves to life his live above all for God, and yet on not so infrequent occasions does things objectively inconsistent with taking God as the rule for one's life, is like the man in the example above, who resolves to live for his family, and yet fails at certain times to act in consistency with that resolve. If one held that he continues, in fact, to be seeking God as his ultimate end, it seems one would similarly have to say that the acts objectively inconsistent with that end, or at any rate the badness and stupidity of those acts, are not entirely voluntary. Thus they would constitute venial sins by reason of a lack of full voluntariness.

But on this account, would any acts be fully voluntary? I'll return to this question in another post.

Fundamental Option and Salvation

The CDF in Persona Humana (1975) and Pope John Paul II in Reconciliatio et Paenitentia (1984) and in Veritatis Splendor (1993) reject the theological theory of a fundamental option insofar as such a theory is understood or interpreted in a manner that denies the traditional doctrine concerning mortal sin, whereby any one conscious and deliberate grave violation of the moral order, which is rooted upon love of God and neighbor, is enough to separate a person from God.

There are those who go as far as to affirm that mortal sin, which causes separation from God, only exists in the formal refusal directly opposed to God's call, or in that selfishness which completely and deliberately closes itself to the love of neighbor. They say that it is only then that there comes into play the fundamental option, that is to say the decision which totally commits the person and which is necessary if mortal sin is to exist; by this option the person, from the depths of the personality, takes up or ratifies a fundamental attitude towards God or people.

In reality, it is precisely the fundamental option which in the last resort defines a person's moral disposition. But it can be completely changed by particular acts, especially when, as often happens, these have been prepared for by previous more superficial acts. Whatever the case, it is wrong to say that particular acts are not enough to constitute mortal sin.

According to the Church's teaching, mortal sin, which is opposed to God, does not consist only in formal and direct resistance to the commandment of charity. It is equally to be found in this opposition to authentic love which is included in every deliberate transgression, in serious matter, of each of the moral laws.
… A person therefore sins mortally not only when his action comes from direct contempt for love of God and neighbor, but also when he consciously and freely, for whatever reason, chooses something which is seriously disordered (Persona Humana, n. 10, emphasis added).

Two distinct principles are here affirmed. First, the orientation of one's life is not a decision made in abstract from the concrete choices to act in the here-and-now. That to which one ultimately orients of one's life (one's final end) must be, at least virtually, the end of every voluntary human action. If an action is in fact incompatible with one's end, the voluntary performance of that action is implicitly a redirection of one's life towards some other end, with which that choice is compatible. Thus a person who once made a decision to life for God, and then, for the sake of money or pleasure, gravely violates the order of charity, is implicitly redirecting his life towards money, pleasure, or, more likely, towards some broader and vaguer goal, such as "the kind of life I decide on" (in this case one makes oneself, rather than God, the ultimate measure of one's life).

Secondly, Persona Humana affirms not only that one's fundamental orientation can be changed by concrete choices, but that one individual concrete choice of something gravely disordered can change one's orientation. (Note, however, that it does not very clearly affirm that one individual choice totally on its own can change one's orientation, though it suggests it by the wording "especially when, as often happens, these [particular acts] have been prepared for by previous more superficial acts."

Later Statements

The same principles are affirmed in Reconciliation and Penance, n. 17: (1) "Mortal sin exists also when a person knowingly and willingly, for whatever reason, chooses something gravely disordered. In fact, such a choice already includes contempt for the divine law, a rejection of God's love for humanity and the whole of creation; the person turns away from God and loses charity."  The concrete choice to do things that are incompatible with having God as one's final end, can alter one's orientation to the final end. (2) "Thus the fundamental orientation can be radically changed by individual acts." A single act may suffice for this change of orientation.

And again, in Veritatis Splendor, n. 68:

Man does not suffer perdition only by being unfaithful to that fundamental option whereby he has made "a free self-commitment to God" (Dei Verbum, 5; cf. Persona Humana, n. 10) . With every freely committed mortal sin, he offends God as the giver of the law and as a result becomes guilty with regard to the entire law (cf. Jas 2:8-11); even if he perseveres in faith, he loses "sanctifying grace", "charity" and "eternal happiness" (cf. Reconciliatio et Paenitentia, 17)

Veritatis Splendor, n. 70, quotes the section of Reconciliatio et Paenitentia that we quoted above, reaffirming this teaching.

Pope Benedict XVI, Spe Salvi

Pope Benedict in Spe Salvi takes a position that sounds quite similar to the theory of a fundamental option. He is speaking directly about salvation or damnation, but in accordance with the teaching of the Church that "to die in mortal sin without repenting and accepting God's merciful love means remaining separated from him for ever by our own free choice" (Catechism of the Catholic Church, n. 1033), what he says has implications about mortal sin.

Persona Humana says, "There are those who go as far as to affirm that mortal sin, which causes separation from God, only exists in the formal refusal directly opposed to God's call, or in that selfishness which completely and deliberately closes itself to the love of neighbor" (emphasis added).

Pope Benedict XVI says in Spe Salvi:

With death, our life-choice becomes definitive—our life stands before the judge. Our choice, which in the course of an entire life takes on a certain shape, can have a variety of forms. [While this does not actually imply that an individual choice doesn't, or doesn't frequently alter one's "life-choice", it does suggest it to some extent.] There can be people who have totally destroyed their desire for truth and readiness to love, people for whom everything has become a lie, people who have lived for hatred and have suppressed all love within themselves. [This sounds very much like the position of the theologians mentioned in Persona Humana.] This is a terrifying thought, but alarming profiles of this type can be seen in certain figures of our own history. In such people all would be beyond remedy and the destruction of good would be irrevocable: this is what we mean by the word Hell (cf. Catechism of the Catholic Church, 1033-1037). On the other hand there can be people who are utterly pure, completely permeated by God, and thus fully open to their neighbors—people for whom communion with God even now gives direction to their entire being and whose journey towards God only brings to fulfillment what they already are (cf. Catechism of the Catholic Church, 1023-1029).

46. Yet we know from experience that neither case is normal in human life. For the great majority of people—we may suppose—there remains in the depths of their being an ultimate interior openness to truth, to love, to God. In the concrete choices of life, however, it is covered over by ever new compromises with evil—much filth covers purity, but the thirst for purity remains and it still constantly re-emerges from all that is base and remains present in the soul. What happens to such individuals when they appear before the Judge? Will all the impurity they have amassed through life suddenly cease to matter?
47…
In this way the inter-relation between justice and grace also becomes clear: the way we live our lives is not immaterial, but our defilement does not stain us for ever if we have at least continued to reach out towards Christ, towards truth and towards love. Indeed, it has already been burned away through Christ's Passion. At the moment of judgment we experience and we absorb the overwhelming power of his love over all the evil in the world and in ourselves. (Pope Benedict XVI, Spe Salvi – emphasis added)

The Pope seems to be saying that those persons who have not descended so far as to have "totally destroyed their desire for truth and readiness to love," and who "have lived for hatred and have suppressed all love within themselves," have not definitively rejected Christ, but are living in such a way that he is still their final end, though their orientation towards this end is covered up (contradicted?) by numerous concrete choices they make and actions they perform, and that they will be saved, though "as through fire." Unless we posit a moment of revelation and conversion in the very instant of death or afterward, this would imply that the "great majority of people" is not in a state of mortal sin.

Do any of my readers know of passages from Pope Benedict XVI/Cardinal Ratzinger that would shed light on his understanding of a fundamental option/life-choice?

In a coming post or posts I'll try to delve into some of the difficulties from a Thomistic perspective.

Perfect Contrition and the Sacrament of Penance

I was struck today by a potentially misleading formulation in the Catechism of the Catholic Church regarding the necessity of intending to confess one's sins in the Sacrament of Penance.

A certain inseparability of remission of sins and the Sacrament of Penance is taught by the Council of Trent and by Pope John Paul II:

Council of Trent

Docet praeterea etsi contritionem hanc aliquando charitate perfectam esse contigat hominem que Deo reconciliare priusquam hoc sacramentum actu suscipiatur ipsam nihilominus reconciliationem ipsi contritioni sine sacramenti voto quod in illa includitur non esse adscribendam.

[The Council] teaches, further, that although this contrition is sometimes perfected by charity and reconciles man with God before this sacrament [of confession] is actually received, this reconciliation is still not to be ascribed to that contrition without the intention of receiving the sacrament [sacramenti voto] that is included in that contrition.

God willed reconciliation to take place in Christ and in his Mystical Body, the Church, in a visible manner. True repentance for sin and love for God implies a desire to accept God's will in this, as in other matters. Hence it includes a desire to sensibly receive reconciliation, in the instrument instituted by Christ, namely sacramental confession. The Council, responding to the Protestant position, insists that one must make reference to this means established by Christ in giving an account of how reconciliation now takes place in Christ.

Reconciliation and Penance (Pope John Paul II)

This same understanding is presented by John Paul II from a pastoral point of view in Reconciliatio et Paenitentia (Reconciliation and Penance). For the believer, the doctrine about the sacrament of confession has as a practical consequence that one desire to receive the grace of reconciliation in an "incarnate" manner, that is in the sacrament.

The first conviction is that for a Christian the sacrament of penance is the primary way of obtaining forgiveness and the remission of serious sin committed after baptism. Certainly the Savior and his salvific action are not so bound to a sacramental sign as to be unable in any period or area of the history of salvation to work outside and above the sacraments. But in the school of faith we learn that the same Savior desired and provided that the simple and precious sacraments of faith would ordinarily be the effective means through which his redemptive power passes and operates. It would therefore be foolish, as well as presumptuous, to wish arbitrarily to disregard the means of grace and salvation which the Lord has provided and, in the specific case, to claim to receive forgiveness while doing without the sacrament which was instituted by Christ precisely for forgiveness.

Catechism of the Catholic Church

The Catechism of the Catholic Church seems to make an attempt to simplify the teaching:

1452 Contritio cum ex amore provenit Dei super omnia amati, « perfecta » appellatur (caritatis contritio). Talis contritio veniales remittit defectus; etiam veniam obtinet peccatorum mortalium, si firmum implicat propositum ad confessionem sacramentalem recurrendi quam primum possibile sit. (Cf Concilium Tridentinum, Sess. 14a, Doctrina de sacramento Paenitentiae, c. 4: DS 1677.)

1452 When it arises from a love by which God is loved above all else, contrition is called "perfect" (contrition of charity). Such contrition remits venial sins; it also obtains forgiveness of mortal sins if it includes the firm resolution to have recourse to sacramental confession as soon as possible. (Cf. Council of Trent (1551): DS 1677.)

However, this way of expressing the need for the sacrament of Penance is potentially quite misleading. Rather than saying something along the lines of "it also obtains forgiveness of mortal sins–genuine contrition includes the firm resolution etc." it says that contrition arising from love of God above all things (charity) "obtains forgiveness of mortal sins if it includes the firm resolution etc." The intention of the author(s) of this text may have been to say, in a subtle way, "one who is really contrite and loves God above all things will desire to observe the visible expression of reconciliation established by God (the Sacrament of Penance); one who is unwilling to observe this visible expression is deceiving himself if he thinks that his contrition is genuinely motivated by love of God." But as it stands, the text suggests that it is possible to have contrition arising from charity, and yet remain burdened by unforgiven mortal sin. This is practically a contradiction in terms, since charity is friendship with God, and a share in God's own love and life, while mortal sin consists in the loss of the divine life in us, and in separation from God. Moreover, if we granted that it were possible to have charity without sins being forgiven, in the event that one was not resolved to have recourse to sacramental confession, we would, in effect, be treating the sign of reconciliation with God (the Sacrament) as more important than the reality of friendship with God and participation in his life (charity).

Aquinas on Sexual Sins – The Dangers of Speaking Formally

Which is worse: adultery or masturbation? Rape or masturbation? Did Aquinas teach that masturbation is a greater sin than rape, because masturbation is unnatural, and rape is not? If so, what did he mean by speaking in this? The suggestion that masturbation is ultimately a greater sin than adultery or rape is immediately repellent to us. In fact it is ridiculous, yet certain authors attribute precisely this position to Thomas Aquinas, reading him to be saying that the sin of masturbation is simply speaking, ultimately, worse than the sins of adultery and rape. Moreover, the further argument is made that the Church upheld this position for a long time, and this (false claim) is used to attack the Church's credibility in sexual ethics. Doubt is sometimes expressed regarding various teachings or practices of the Church, e.g., regarding the Church's affirmation that homosexual intercourse is wrong, or the restriction of priestly ordination in the Roman Rite to those who freely choose to embrace celibacy. The argument is made that if the Church "taught for a thousand years that masturbation is a worse sin than rape", its teaching on sexual matters can't be very sound.

This misunderstanding of the Church's traditional teaching on sins against nature seems to be more prevalent than I realized. I hadn't previously realized how many authors and teachers assert that not only many medieval theologians, but even Thomas Aquinas taught this. Here are some sample quotes from books discussing masturbation in Aquinas:

[In Aquinas's view], Because sins against nature were sins against God, they were considered more serious than sins against other people, such as adultery, seduction, and rape (John F. Schumaker, Religion and Mental Health [Oxford University Press US], 1992), 76).To make his point perfectly clear, Aquinas poses a question: are not rape and adultery worse than unnatural acts, since they harm other persons, while consensual sins against nature do not? The answer is unequivocal: the four non-procreative forms of sex are worse, since–though not harmful to others–they are sins directly against God himself as the creator of nature. According to this logic, rape, which may at least lead to pregnancy, becomes a less serious sin than masturbation (Louis Crompton, Homosexuality and Civilisation, [Harvard University Press, 2006], 188).

"A practice opposed to the pattern set for us by nature" exceeds in wickedness the seduction of an innocent of the opposite sex, adultery, and rape (II-II 154:12) (Sex from Plato to Paglia, by Alan Soble [Greenwood Publishing Group, 2006], 1053).

One unfamiliar with the scholastic manner of speaking formally about an issue, that is, addressing precisely the question at hand, might easily get this impression from Aquinas's treatment of sexual "sins against nature."

Here is the text itself. In the Summa Theologiae II-II, q. 154, a. 12, Aquinas says:

In each kind of thing the worst corruption is the corruption of the principle on which other things depend. Now the principles of reason are the things in accord in nature… and therefore, to act against what is determined by nature, is most serious and base. Therefore since in the sins against nature man transgress what is determined by nature in regard to sex, the sin in this matter is the gravest kind of sin. After this is incest… while by the other species of lust one transgresses only that which is determined according to right reason, but presupposing the natural principles. But it is more contrary to reason to have sex not only contrary to the good of the offspring to be born, but also with injury to another. And therefore simple fornication, which is committed without injury to another person, is the least kind of lust.

The first objection of the article argues that sins against nature are not the worst, because they are not the most contrary to charity: "The more a sin is contrary to charity the graver it is. Now adultery, seduction and rape, which are injurious to our neighbor, seem to be more contrary to the love of our neighbor, than unnatural sins, by which no other person is injured. Therefore sin against nature is not the greatest among the species of lust." St. Thomas replies to this objection: "As the order of right reason is from man, so the order of nature is from God himself. And therefore in sins against nature, in which the very order of nature is violated, injury is done to God himself, the one who ordains nature."

Aquinas is focusing on the sins precisely as a violation of the right use of sexuality, and abstracting from other aspects of them. As justice is a greater virtue than chastity, so injustice is a greater evil than unchastity, and thus all things considered, Aquinas would consider rape a greater evil than masturbation or contraception. This formal way of speaking is recognized by some more considerate authors:

The teaching of medieval theologians that such sexual sins as masturbation, sodomy, and contraception are more perverse, as sexual sins, than fornication or adultery or even rape (the former were said to be contra naturam whereas the latter were said to be praeter naturam), angers many people today. But this teaching must be understood properly. The medieval theologians are claiming that certain kinds of sexual sins more seriously offend the virtue of chastity than do others. They are not saying that these sins are for this reason less grave as sins than adultery or rape, for instance. After all, adultery and rape are very serious violations of the virtue of justice as well as being violations of the virtue of chastity. Thus, as a sin, rape is far more serious than masturbation or homosexual sodomy because it not only offends chastity but also gravely violates justice. (Ronald David Lawler, Joseph M. Boyle, William E. May, Catholic sexual ethics: a summary, explanation & defense).

It is important to understand this formal way of speaking, considering one aspect of human behavior and abstracting from other aspects. But as Aquinas himself says in another context, "where such a manner of speaking is found in the writings of an authority, one should not continue to speak in this manner, but should piously explain what is said" (Summa Theologiae I, q. 31, a. 4, loose translation).

In regards to the comparison between fornication and masturbation, St. Thomas may have in mind fornication in an instance where there is a potential marriage between the two persons (even if they are not engaged), since otherwise it would be contrary to the good of the offspring who might be born. Whether he had this in mind or not, it does seem to me that there are many cases where fornication is worse than masturbation, on account of the harm done to the other party, and on account of the potential harm of children conceived and born as a result (e.g., if they are thereby deprived of the presence of one parent in the home).

The Reception of Thomas Aquinas

I would agree that Thomas Aquinas's classification of sins as received by moralists in following centuries became a problem, in part because it was not used formally, but materially; that is, the descriptions of sins and the various gravity of different sins or aspects of sins were applied directly to physical, material acts. Even Alphonsus Liguori, named the patron of confessors and moralists by Pope Pius XII, seems to have fallen into this error. And in this respect I do see problems with the Church's usual approach to sexual morality for centuries, not sexual morality in particular however, but simply morality in general, the tendency being to take an extrinsic, legalistic approach to morality, and to focus on sins, rather than an approach focused on the real nature of human goods. This was to some extent an outgrowth of nominalism, which made of natural law a kind of arbitrary imposition by God's will. In another post I'll come back to this general topic of legalistic morality.

Update:

I gather from the questions that bring people to this post that this anachronistic reading of Thomas Aquinas (and the other scholastics) is a common one. Aside from some general queries such as "contra naturam in Aquinas," or "Aquinas' thoughts on rape," or "Aquinas on sexual morality," "Thomas Aquinas on masturbation," "Aquinas' views on rape," there are a number of questions that suggest having encountered such a view:

1. When did rape become worse than masturbation? (Related questions: Rape is not as bad as masturbation? Is masturbation a greater sin than rape? Masturbation worse than incest? Which is worse, masturbation or adultery?)

It was all along. But if the question is meant in the sense "when did people stop making technical lists of how fundamentally an act goes against the sexual purpose of the genital organs?", the answer is, "when they in general stopped making such technical lists."

2. Is masturbation worse than fornication? (Similar related queries: Is masturbation a greater sin than having sex? [This must mean "having sex" outside of a marital relationship.]; is masturbation better or worse than actual intercourse?)

In most cases not. First, as noted above, in the many cases where the present relationship or the capacity for a committed and unselfish relationship in the future is seriously harmed, or where danger to offspring is present, fornication is objectively graver. Moreover, masturbation requires, and in most cases involves, a much less deliberate act of will than fornication does, and therefore the sin is any case subjectively less bad.

3. The catholic church taught that masturbation is worse than rape because at least the latter might result in conception. (Related questions: Rape is much less a sin than masturbation. Masturbation is worse than rape? [Did] Aquinas [teach that] rape is better than masturbation?)

No, it didn't.

4. Is masturbation worse than adultery?

No.