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Saint Alphonsus Liguori on Marital Chastity


Saint Alphonsus Liguori was a Catholic Bishop who lived from 1696 to 1787. He died at the age of 90 years. He was canonized by Pope Gregory XVI, and was proclaimed a Doctor of the Church by Pope Pius IX. He is the patron Saint of confessors and of moral theologians.

The work titled "Moral Theology" by Saint Alphonsus Liguori contains a few brief passages on marital chastity, that is to say, on which types of sexual acts are permissible in marriage. Of course, all sexual acts are prohibited outside of marriage.

The work in question is ten thick volumes entirely in Latin. The work is a review of opinions by theologians on various moral questions. A question is stated, and then differing answers found among various authors are explained. However, the vast majority of these authors and their cited works are lost in obscurity. The main purpose of the work is to survey opinions of Catholic theologians and authors on various topics in moral theology. So the mere fact that a position is stated in "Moral Theology" does not imply the opinion is sound. Even so, at certain points in the work, Saint Alphonsus Liguori states his own understanding of the topic, rejecting one answer and affirming another.

1: On Matrimony, Book VI, n. 491-492

St. Alphonsus considers a question on marital sexual acts:

Latin: An autem sit semper mortale, si vir immittat pudenda in os uxoris?
Translation: "Or whether it is always [a] mortal [sin], if the husband were to insert [his] penis into the mouth of [his] wife?"

Then, the Saint gives an answer proposed by some moral theologians of his day:

Latin: Negant ... modo absit periculum pollutionis.
Translation: "In the negative [say several authors] ... but only if there is no danger of pollution."

Some theologians of that time period (1700's) claimed that it would be moral, only if there was no danger that the husband would climax ("danger of pollution"). But then the Saint rejects their answer and gives an answer he asserts to be the truth:

Latin: Sed verius affirmant ... tum quia in hoc actu ob calorem oris adest proxiumum periculum pollutionis, tum quia haec per se videtur nova species luxuriae contra naturam (dicta ab aliquibus irrumatio)
Translation: "But the truth is in the affirmative [citing several authors] ... not only because, in this act, on account of the warmth of the mouth, there is proximate danger of pollution, but also because this [act] is considered [to be], in itself, an abnormal type of pleasure against nature (as has been said of any type of shameful sex)."

Saint Alphonsus asserts that this type of act, within marriage is a mortal sin for two reasons. First, because there is always the danger of pollution, i.e. the risk that the husband will climax, making the act a completed unnatural sexual act. Second, because this type of act, even without climax, is "in itself ... against nature", which means that it is an intrinsically evil and gravely immoral sexual sin. And he asserts that the same is true of "any type of shameful sex", that is to say, any type of unnatural sexual act.

Canon Law defines the natural sexual act in explaining the consummation of a marriage. A marriage that is ratified by the consent of the spouses (at the wedding ceremony) is afterward consummated only "if the spouses have performed between themselves in a human fashion a conjugal act which is suitable in itself for the procreation of offspring, to which marriage is ordered by its nature and by which the spouses become one flesh." [Canon 1061, n. 1]. Even if one or both spouses are infertile for some reason, the act is still termed natural, if it is the type of act that would be capable of procreation if they were fertile.

The moral object of any act is the end toward which the knowingly chosen act is inherently ordered, regardless of whether the moral object is attained. To be moral, each and every sexual act must be marital, unitive, and procreative. Sexual relations open to life is inherently ordered toward the procreative meaning, and so it is called the natural act.

An unnatural sexual act is any type of sex, whether or not climax occurs, which is not ordered, by the nature of the act, toward procreation. Unnatural sexual acts are not procreative. Neither are they truly unitive (even if there exists a merely physical type of union in the act), since these acts do not offer the type of union ordained by God for husband and wife.

Then the Saint adds some commentary after his answer:

Latin: Semper enim ac quaeritur a viro aliud vas, praeter vas naturale, ad copulam institutum, videtur nova species luxuriae.
Translation: "And besides, whenever another orifice [or vessel] is sought by the husband, other than the natural orifice, which has been ordained for copulation, it is considered [to be] an abnormal type of [sexual] pleasure."

The term "vessel" [vas] in Latin texts of moral theology refers to any orifice or receptacle used in a sexual act. The natural vessel is the vagina of the wife. Unnatural vessels include any other orifice or body part used to commit a sexual act (even if it is not strictly speaking an orifice).

2: On Matrimony, Book VI, Q. 919

Latin:An autem, si vir se retrahat post seminationem, sed ante seminationem mulieris, possit ipsa statim tactibus se excitare, ut seminet?
Translation: "Then, if the husband withdraws after climax, but before the climax of the wife, whether it is possible for her to immediately excite herself with touches so as to climax?"

Latin: Ratio, quia semen mulieris non est necessarium ad generationem; item quia effusio illa mulieris, utpote separata, non fit una caro cum viro.
Translation: "The reason: because the climax of the wife is not necessary to procreation; also, because this sexual pleasure of the wife, in as much as they are separated, does not occur as one flesh with the husband."

Saint Alphonsus Liguori cites several authors answering "No". He agrees with this answer, explaining the reason. First, the climax of the wife is not essential to procreation, as it is for the husband. So her act, in exciting herself with touches after his withdrawal (after natural marital relations has ended) lacks the procreative meaning of sex. Second, the sexual pleasure of the wife, if it is obtained while they are separated, also lacks the unitive meaning of sex.

In modern terms, for any sexual act to be moral, the act must be ordered inherently toward three goods: the marital, unitive, and procreative meanings. But in the act considered here, the wife carries out a sexual act which is absent of the unitive and procreative goods. In fact, because it is not unitive or procreative, her act is nothing other than masturbation (even if it is her husband who touches her). And such an act is also not truly marital. It is not the type of sexual act God intends for Christian spouses.

Latin: sed haec ratio non suadet, nam si hoc permitteretur uxiborus deberet permitti etiam viris
Translation: "This reason is not persuasive, for if this is permitted to wives, it ought to be permitted also to husbands."

Saint Alphonsus then cites some authors who answer the question "Yes", but he rejects their answer, explaining that their reason is not persuasive. For it were moral for the wife, it would be moral for the husband. There are not two separate versions of the eternal moral law in the marital bedroom, one for the wife and a different one for the husband. So Saint Alphonsus agrees with the authors who answered "No". Clearly, the Saint rejected the idea of a wife using any technique, whether touches or any other means, to reach climax, after the husband withdraws. For then the two are not one flesh, and so the unitive meaning is absent from the sexual act. In addition, such a sexual act apart from union is also not procreative. The absence of the unitive and procreative meanings is what makes such a sexual act gravely immoral.

Alphonsus does not accept the idea that the wife has a right to obtain sexual pleasure, regardless of the means, as some modern authors imply. Neither does the Saint treat the subsequent act of the wife and the prior act of natural marital relations as if these together constituted "one act", as other modern authors have claimed.

Moreover, the reasons given by the "No" response, which is the response of the Saint, are completely in accord with the recent teachings of the Magisterium that "each single act", that is to say, "each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life" and that there is an "inseparable connection, established by God, which man on his own initiative may not break, between the unitive significance and the procreative significance which are both inherent to the marriage act." [Pope Paul VI, Humanae Vitae, n. 3, 11, 12]

3: On Matrimony, Book VI, Q. 916

In this question, Saint Alphonsus rejects the proposition, so often asserted today, that the married couple may use unnatural sexual acts, as long as the husband completes the act (i.e. climaxes) only in a subsequent act of natural marital relations.

Latin: An peccet mortaliter vir inchoando copulam in vase praepostero , ut postea in vase debito eam consummet?
Translation: "Whether it is a mortal sin for the husband to begin copulating in a disordered [or perverse] orifice, then afterward consummate the act in the proper orifice?"

This is exactly the idea proposed by foolish commentators today. They claim that all manner of unnatural sexual acts (oral, anal, manual "stimulation") are justified as long as the husband "completes" the act by climaxing in a subsequent act of natural marital relations. And what answer does Saint Alphonsus give to the question?

First, notice that the question asks if this proposal is a mortal sin. As usual, the Saint cites opinions on both sides of the question, first citing some who say "No", it is not a mortal sin, as long as there is no "danger of pollution" (i.e. danger of the husband climaxing during the unnatural sexual act), and others who say that there is no mortal sin in any sexual acts between the spouses. But the Saint rejects these opinions.

Saint Alphonsus says: "But they [other cited authors] affirm, commonly and correctly," that it is a mortal sin. So the Saint states that the correct opinion, which was also the common opinion of the theologians of his day, is that such acts are gravely immoral. The reason he gives is quite compelling.

Latin: Ratio, quia ipse hujusmodo coitus (etsi absque seminatione) est vera sodomia, quamvis non consummata, sicut ipsa copula in vase naturali mulieris alienae est vera fornication , licet non adsit seminatio.
Translation: "The reason is that this manner of his sexual act (even without climax) is truly sodomy, whether or not it is consummated, just as an act of copulation in the natural orifice of another woman is truly fornication, even if there is no climax."

So Saint Alphonsus Liguori rejected the idea that unnatural sexual acts are moral to use as foreplay, as long as the husband consummates only in a subsequent natural act. And yet this rejected idea continues to be promoted today, mostly by Catholics who hide behind the anonymity of the internet.


Many different excuses are being used today to give approval to the use of unnatural sexual acts within the Sacrament of holy Matrimony. And whether I present the teachings of Saint Augustine and Saint Aquinas (See this article), or of present-day theologians (same article), or the answers given by Saint Alphonsus, I know that some readers will use the flimsiest excuses to dismiss whatever is said, no matter how compelling. But if anyone offers them a way to justify this type of sin, no matter how ridiculous, they adopt it as if it were dogma.

The first principle of ethics is a sincere conscience, which seeks moral truth with severe intellectual honesty. In most discussions on sexual ethics in general and marital ethics in particular, the persons arguing for the approval of illicit acts lack this sincerity. I suppose that many of these promoters of unnatural sexual acts are themselves committing unnatural sexual acts in their marriages. That is why they seek a theological rationalization for their sins, and why they try so hard to convince others to commit the same sins (to make the behavior seem acceptable). And it is true, but very sad to say, that no theological argument carries any weight with them. They do not accept correction for their sins -- neither from the Saints, nor from the Magisterium, nor from Sacred Scripture.

Teachers will have the stricter judgment (cf. James 3:1).

If a married couple unfortunately commit these types of gravely immoral acts, they are responsible before God for their private sins. But when Catholics go online to loudly and repeatedly promote the use of gravely immoral sexual acts within marriage, thereby influencing many marriages (not just their own marriage), the harm is multiplied many times over, and so is the culpability. It is a much graver sin to influence many persons to sin mortally, than to commit a single mortal sin yourself. If you sin yourself, you might repent and go to Confession. But if you cause others to sin gravely, and you later repent, how will you undo the damage to those souls?

These false teachers who use the internet to convince many Catholics to sin gravely against the Sacrament of Marriage and against their own bodies will be severely punished by God.

{13:4} May marriage be honorable in every way, and may the marriage bed be immaculate. For God will judge fornicators and adulterers.

More Reading: The Catholic Marriage Bed

Ronald L. Conte Jr.
Roman Catholic theologian and translator of the Catholic Public Domain Version of the Bible.

Please take a look at this list of my books and booklets, and see if any topic interests you.

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