Can spouses sin sexually with each other in their sexual acts?
There are three main reasons for why the Natural Law, The Holy Bible, Apostolic Tradition, as well as the Church and Her Popes and Saints (as we will see) teaches that all spouses who perform unnecessary and non-procreative forms of sexual acts (such as masturbation of self or of spouse, oral and anal sex, foreplay, and sensual touches and kisses) either by themselves or in relationship to the marital act before, during or after it, are sinning mortally against their conscience and the Divine and Natural Law instituted by God.
The first reason is that they are a kind of drug abuse since they are selfish, intoxicating and unnecessary just like drug abuse is;the second is that they are shameful since the people who commit these unnecessary acts are ashamed to do them in front of other people; and the third is that they are non-procreative even though God’s law teaches that the “the conjugal act is destined primarily by nature for the begetting of children”. (Pope Pius XI) These three reasons are also why the Church teaches that even the normal, natural and procreative “act of marriage exercised for pleasure only” is condemned as a sin for both the married and unmarried people alike (Blessed Pope Innocent XI) and why this truth was taught already in the Old Testament by God long before even the New Testament was revealed to us by Our Lord Jesus Christ.
The Holy Bible, Tobias 6:16-17, 22; 8:9 “Then the angel Raphael said to him [Tobias]: Hear me, and I will shew thee who they are, over whom the devil can prevail. For they who in such manner receive matrimony, as to shut out God from themselves, and from their mind, and to give themselves to their lust, as the horse and mule, which have not understanding, over them the devil hath power. … And when the third night is past, thou shalt take the virgin with the fear of the Lord, moved rather for love of children than for lust, that in the seed of Abraham thou mayest obtain a blessing in children… [Tobias said] And now, Lord, thou knowest, that not for fleshly lust do I take my sister to wife, but only for the love of posterity, in which thy name may be blessed for ever and ever.”
The first reason for why all non-procreative and unnecessary forms of sexual acts are mortally sinful is that all sexual acts (even marital, natural, lawful and procreative ones) are intoxicating and affects the person similar to the effect of a drug. In fact, the sexual pleasure is many times more intoxicating than many drugs that are unlawful to abuse. But when people are performing unnatural and non-procreative forms of sexual acts, they are abusing the marital act in a similar way that a drug user abuses drugs, or a glutton abuses food. It is an inherently selfish act that are not founded on reason, but only on their unlawful and shameful search for carnal pleasure, similar to the action of a person that uses drugs in order to get intoxicated or high.
This is also why the Church teaches that even the normal, natural and procreative “act of marriage exercised for pleasure only” is condemned as a sin for both the married and unmarried people alike (Pope Innocent XI, Various Errors on Moral Matters Condemned in Decree (# 8), March 4, 1679). Since the Church and the Natural Law condemns even the normal, natural and procreative “act of marriage exercised for pleasure only”, even though this act is procreative in itself, it is obvious that all non-procreative and unnecessary forms of sexual acts (such as sensual kisses and touches) are condemned as even worse sins (that is, as mortal sins) – since they are utterly unnatural, unreasonable, shameful, and selfish.
A sick person is allowed by God’s permission to take drugs in order to lessen his pain. But when this sick person uses more drugs than he needs in order to get intoxicated, or continues to use the drugs after he gets well, he commits the sin of drug abuse. This is a perfect example of those who perform non-procreative forms of sexual acts either by themselves or in relationship to the marital act. They are gluttonous or overindulgent in the marital act, and are thus sinning against their reason and the Natural Law. For “the sin of lust consists in seeking venereal pleasure not in accordance with right reason...” and “lust there signifies any kind of excess.” (St. Thomas Aquinas, Summa Theologica, Second Part of the Second Part, Q. 154, Art. 1)
The “excess” that St. Thomas and the Church condemns as a sin are all sexual acts except for what is inherent in the normal, natural and procreative marital act itself. All other sexual acts are by their own nature inexcusable and a sin against the Natural Law, which means that even though a person has never been told or taught that they are sins, they are still committing a mortal sin, just like a person do not have to be told or taught that murder, abortion, stealing, or getting intoxicated or drunk is a sin against the Natural Law in order for this person to be able to commit a mortal sin. As the Haydock Bible and Commentary correctly explains about The Natural Law and Romans 2:14-16: “these men are a law to themselves, and have it written in their hearts, as to the existence of a God, and their reason tells them, that many sins are unlawful...”
In truth, “We may also reply that "lasciviousness" relates to certain acts circumstantial to the venereal act, for instance kisses, touches, and so forth.” (Summa Theologica, II-II, Q. 154, Art. 1) Notice that St. Thomas even rejects as lascivious and unlawful “acts circumstantial to the venereal act, for instance kisses, touches, and so forth” and so it is clear that St. Thomas taught that all non-procreative and unnecessary sexual acts are sinful and against nature. This is also why the Natural Law and the Church teaches that even sensual kisses performed “for the sake of the carnal and sensible delight which arises from the kiss” is condemned as a mortal sin for both the married and the unmarried people alike (Pope Alexander VII, Various Errors on Morals Condemned in Decree #40, September 24, 1665; Denz. 1140).
Can a sick person who only need one pain killer tablet to ease his pain claim that he can take more tablets in order to get intoxicated or high and escape the sin of drug abuse? Of course not! But this is the kind of unnatural and idiotic logic we have to deal with from those perverse, evil and damned persons who defend such vile sexual acts against God and nature as foreplay, and anal, oral, and manual sexual acts. Not only are these acts in themselves abominable and a kind of drug abuse – and thus a mortal sin – but just like drug addicts they add a lie to their mortal sin of drug abuse when they claim that they need or are entitled to perform such acts and thus derive more sexual pleasure than nature and God allows them to have.
Venerable Luis de Granada (1505-1588): “Those that be married must examine themselves in particular, if in their mind thinking of other persons, or with intention not to beget children, but only for carnal delight, or with extraordinary touchings and means, they have sinned against the end, and honesty of marriage.” (A Spiritual Doctrine, containing a rule to live well, with divers prayers and meditations, p. 362)
Since all humans knows by instinct and nature that one may not get intoxicated for selfish or unnecessary reasons, it is clear that both the married as well as the unmarried people who perform non-procreative or unnecessary sexual acts are in a state of damnation, since they are sinning mortally against both nature and their own reason. “For necessary sexual intercourse for begetting [of children] is free from blame, and itself is alone worthy of marriage.But that which goes beyond this necessity [of begetting children, such as sensual kisses and touches] no longer follows reason but lust.” (St. Augustine, On the Good of Marriage, Section 11)
Just like in the case of the person who use drugs, one must have an absolutely necessary reason for using the drugs, such as an illness, and motives that aren’t absolutely necessary such as “love”, “pleasure” or “fun” can never be used as an excuse to excuse the marital act, just like one cannot use such unnecessary and evil excuses for the purpose of excusing one’s drug abuse. In this context of speaking about the truth that the vehemence of the marital sexual act is “more oppressive on the reason than the pleasures of the palate”, St. Thomas shows that the sexual act is intoxicating and thus oppressive on the reason just like a drug is, which shows us that it is a fact of the Natural Law and the Law of the Church that the marital sexual act must be excused by the absolutely necessary motive of procreation just like the drug use must be excused with an absolutely necessary motive.
St. Thomas Aquinas, Summa Theologica, Second Part of the Second Part, Q. 153, Art. 2: “Venereal pleasures are more impetuous, and are more oppressive on the reason than the pleasures of the palate: and therefore they are in greater need of chastisement and restraint, since if one consent to them this increases the force of concupiscence and weakens the strength of the mind. Hence Augustine says (Soliloq. i, 10): ‘I consider that nothing so casts down the manly mind from its heights as the fondling of women, and those bodily contacts which belong to the married state.’”
Here we see the very evident truth from the Natural Law that the sexual act deprives people of the ability to reason, explained in a very eloquent way by The Angelic Doctor. In another section of his Summa, he explains this truth about the marital sexual act again:
St. Thomas Aquinas, Summa Theologica, Supplement, Q. 49, Art. 1: “Now there is a loss of reason incidental to the union of man and woman, both because the reason is carried away entirely on account of the vehemence of the pleasure, so that it is unable to understand anything at the same time, as the Philosopher says (Ethic. vii, 11); and again because of the tribulation of the flesh which such persons have to suffer from solicitude for temporal things (1 Corinthians 7:28). Consequently the choice of this union cannot be made ordinate except by certain compensations whereby that same union is righted, and these are the goods which excuse marriage and make it right.”
Therefore, the normal, natural and procreative marital act performed by two married spouses is the only sexual act that can be excused from sin since man knows by nature and instinct that one must excuse an act of intoxication with an absolutely necessary motive. Anything contrary to this is unnatural and evil.
St. Thomas Aquinas, Summa Theologica, Supplement, Q. 49, Art. 5: “Whether the marriage act can be excused without the marriage goods [sacrament, fidelity, procreation]? On the contrary, If the cause be removed the effect is removed. Now the marriage goods are the cause of rectitude in the marriage act. Therefore the marriage act cannot be excused without them. Further, the aforesaid act does not differ from the act of fornication except in the aforesaid goods. But the act of fornication is always evil. Therefore the marriage act also will always be evil unless it be excused...”
In this context, St. Thomas Aquinas taught the following concerning the vice of sexual intemperance and how the “the reason is absorbed” when one performs unlawful sexual acts: “Among the vices of intemperance, venereal sins are most deserving of reproach, both on account of the insubordination of the genital organs, and because by these sins especially, the reason is absorbed.” (Summa Theologica, Second Part of the Second Part, Q. 151, Art. 4, Reply to Objection 3, Whether purity belongs especially to chastity?)
When married spouses do not excuse the marital act (which is intoxicating in a way similar to a drug) with the honorable motive of begetting children by only performing the normal, natural and procreative marital act, they perform an act that is inherently sinful, selfish, unreasonable, and unnatural since “the conjugal act is destined primarily by nature for the begetting of children” (Pope Pius XI, Casti Connubii, # 54) and since “the act of marriage exercised for pleasure only” is condemned as a sin by the Natural Law (Pope Innocent XI). And so, the marital act needs an absolutely necessary excuse to legitimize and make moral the inherently evil act of getting intoxicated just like one needs an excuse, like a grave illness, to legitimize and make moral the inherently evil act of getting intoxicated by a drug.
An inherently evil act must always be excused with an absolutely necessary motive or purpose. Otherwise, it will always be a sin. Two examples that clearly demonstrates this fact of “excusing” an otherwise evil act are found in the case of a man injuring another person, which is excused in the case of self-defense; or in the case of a man getting intoxicated, which is excused when a man is sick and requires this intoxication in order to get pain relief. All other inherently evil acts than what is absolutely necessary are strictly condemned as sins, since they cannot be excused by an absolutely necessary motive. For example, a man cannot hurt another man if he wants his money, or if he does not like him; and a man cannot get drunk or intoxicated just because he is sad or unhappy, for none of these excuses are absolutely necessary. Thus, these excuses are not enough by themselves to excuse these acts from being sinful. In truth, some evil acts cannot even be excused at all, such as in the case of a man who is suffering from hunger, but who nevertheless is never allowed to kill another person in order to get food to survive. It is thus a dogmatic fact of the Natural Law that “the generative [sexual] act is a sin unless it is excused.” (St. Bonaventure, Commentary on the Four Books of Sentences, d. 31, a. 2, q. 1) It could not be more clear from the Natural Law as well as the teachings of the Church that “Coitus is reprehensible and evil, unless it be excused” (Peter Lombard, Archbishop of Paris, Sententiarum, 3, d. 37, c. 4) and that is also why all who commit the marital act without excusing it, will always commit sin. “Therefore the marriage act also will always be evil unless it be excused...” (St. Thomas Aquinas, Summa Theologica, Supplement, Q. 49, Art. 5)
The second reason for why all non-procreative and unnecessary forms of sexual acts are mortally sinful is that all sexual acts (even marital, natural, lawful and procreative ones) are shameful, which is why people never perform any sexual acts in front of other people.
“Now men are most ashamed of venereal acts, as Augustine remarks (De Civ. Dei xiv, 18), so much so that even the conjugal act, which is adorned by the honesty of marriage, is not devoid of shame… Now man is ashamed not only of this sexual union but also of all the signs thereof, as the Philosopher observes (Rhet. Ii, 6).” (St. Thomas Aquinas, Summa Theologica, Second Part of the Second Part, Q. 151, Art. 4)
And so, when people are performing such inherently shameful acts for lustful and selfish reasons, they are sinning against the Natural Law imprinted on their hearts.
Some people may object that there are many other events that are shameful and that are not yet inherently sinful such as soiling one’s pants or being forced to show oneself naked to other people against one’s own will. This objection however fails to notice the obvious difference between 1) people committing acts of lust with a desire or longing; and 2) events which are shameful but who are not desired or longed for by a person in a sensual way.
Acts of lust are acts performed for the sake of a pleasure and are performed with the will and purpose of satisfying a sensual desire while the events or acts of soiling one’s pants or being forced to show oneself naked to other people is not a desire or lust that is sought after in a sensual way. Thus, these people do not desire that these events should happen. If those people who endured the events of soiling their clothes or naked exhibition against their will would sensually desire or lust for that these shameful events would happen in the same way that a man or a woman lust for and desire that sexual acts or acts of lust happen, they would indeed be declared the most disgusting perverts. Who but a complete and satanic pervert would sensually desire or lust after soiling their pants or being exhibited naked? Thus, it is not just a mere shameful act or event that is sinful, but the shameful act that is performed with the intention of pleasing oneself sensually, that is sinful.
St. Methodius taught that the marital act was “unseemly,” and St. Ambrose agreed with the Holy Bible that it causes a “defilement” (Leviticus 15:16). St. Augustine agreed with the Holy Bible that “It is good for a man not to touch a woman” (1 Corinthians 7:1) and that sexual pleasure, lust or concupiscence for both the married and unmarried people alike are not something “good” or “praiseworthy” but are truly “evil of concupiscence” and the “disease of concupiscence” that arose as an evil result of the original sin of Adam and Eve.
This is also why the Holy Bible urges people to remain unmarried and in a life of chastity since the married man “is solicitous for the things of the world, how he may please his wife: and he is divided” (1 Corinthians 7:33). St. Paul in the Bible also warns those who would marry as opposed to those who would remain virgins that spouses “shall have tribulation of the flesh”: “But if thou take a wife, thou hast not sinned. And if a virgin marry, she hath not sinned: nevertheless, such shall have tribulation of the flesh. But I spare you.” (1Corinthians 7:28) It is certain that St. Paul does not refer to the desire to procreate as a tribulation of the flesh. Consequently, he can be referring only to one thing—sexual pleasure. Indeed, sexual pleasure is a tribulation of the flesh that must hence be fought against in thought and deed in some way or the Devil will succeed in tempting a spouse to fall into mortal sins of impurity either with the other spouse, with himself or with someone other than his spouse. “Nothing so casts down the manly mind from it’s height as the fondling of women and those bodily contacts which belong to the married state.” (St. Augustine of Hippo, The Soliloquies 1:10; cf Summa Theologica, Second Part of the Second Part, Q. 151, Art. 3)
The sexual pleasure is very similar to the effect of a strong drug, and drugs as we all know are very easy to become addicted to by abusing them or overindulging in them. The stronger a drug is, the more is also our spiritual life hindered, and that is why the angelic life of chastity will always be more spiritually fruitful than the marital life according to God’s Holy Word in the Bible. And so, it is clear that Holy Scripture infallibly teaches that marriage and the marital life is an impediment to the spiritual life, while a life of chastity and purity “give you power to attend upon the Lord, without impediment.” (1Corinthians 7:35)
St. Maximus the Confessor (c. 580-662): “Again, vice is the wrong use of our conceptual images of things, which leads us to misuse the things themselves. In relation to women, for example, sexual intercourse, rightly used, has as its purpose the begetting of children. He, therefore, who seeks in it only sensual pleasure uses it wrongly, for he reckons as good what is not good. When such a man has intercourse with a woman, he misuses her. And the same is true with regard to other things and one’s conceptual images of them.” (Second Century on Love, 17; Philokalia 2: 67-68)
Someone might say that it is the sexual member that is shameful or evil to expose to others and not concupiscence or the sexual lust. But this argument is false and easily refuted since no one who is not a complete pervert would have sex in front of other people even though their whole body was covered by sheets or blankets. This proves to us that it is the sexual pleasure that is shameful and evil, and not only the exhibition of the sexual organ. For “man is ashamed not only of this sexual union but also of all the signs thereof,” (St. Thomas Aquinas) and this proves to us that not only the sensual desire is shameful, but also the very sexual act and “also of all the signs thereof”.
St. Jerome: “Thus it must be bad to touch a woman. If indulgences is nonetheless granted to the marital act, this is only to avoid something worse. But what value can be recognized in a good that is allowed only with a view of preventing something worse?”
The sexual pleasure is always an evil pleasure to experience in itself since it is a shameful and intoxicating pleasure that is very similar to the evil pleasure people experience when they abuse alcohol or drugs, and that is why it is always an evil pleasure to experience even for married couples, even though married spouses do not sin during their normal, natural and procreative marital acts since “those who use the shameful sex appetite licitly are making good use of evil.” (St. Augustine, Anti-Pelagian Writings) St. Augustine in his book On Marriage and Concupiscence, explains this evil thus: “Wherefore the devil holds infants guilty [through original sin] who are born, not of the good by which marriage is good, but of the evil of concupiscence [lust], which, indeed, marriage uses aright, but at which even marriage has occasion to feel shame.” (Book 1, Chapter 27)
St. Augustine’s reference to the lawful use of “the shameful sex appetite” means that spouses are only allowed to engage in marital intercourse as long as they perform the act for the sake of conceiving a child. Spouses who perform the marital act without excusing it with the motive or purpose of procreation are thus “making evil use of evil” according to St. Augustine. “I do not say that the activity in which married persons engage for the purpose of begetting children is evil. As a matter of fact, I assert that it is good, because it makes good use of the evil of lust, and through this good use, human beings, a good work of God, are generated.” (St. Augustine, Against Julian, 3.7.15) It is thus obvious that the cause of the shame that is inherent in the sexual act, as we have seen, is “the evil of the sex appetite.” (St. Augustine, Anti-Pelagian Writings)
The third reason for why all non-procreative and unnecessary forms of sexual acts are mortally sinful is that the Natural Law teaches that “the conjugal act is destined primarily by nature for the begetting of children” (Pope Pius XI, Casti Connubii #54) and that even the normal, natural and procreative “act of marriage exercised for pleasure only” is condemned as a sin for both the married and unmarried people alike (Pope Innocent XI, Various Errors on Moral Matters Condemned in Decree (# 8), March 4, 1679).
The Natural Law is rooted in design. God, the Supreme Designer, has imprinted a design on all created things – including the human person, both in his spiritual and physical being – a purpose for which each has been created. Thus, with regard to the human person, the Creator has designed speech for communicating the truth and the mouth to swallow food etc. Likewise, the Creator has designed the sexual organs for something noble, namely, for procreating children. Because of this, the Church’s teaching has always been clear from the beginning that: “the conjugal act is destined primarily by nature for the begetting of children” (Pope Pius XI, Casti Connubii #54).
Any action of the sexual organisms (the private parts) or other acts that are intended to arouse sensuality that is lacking the procreative function, is always sinful and against the Natural Law. An action of the sexual faculties outside of the normal and natural marital act are lacking the procreative dimension and consequently, it would be sexual pleasure sought for itself, isolated from its procreative function – and that is always an unlawful lust. The fact that sinful spouses may engage in the normal, natural and procreative marital act before, during or after they have engaged in another kind of sinful, non-procreative and unnecessary sexual act (such as masturbation of self or of spouse, oral and anal sex, foreplay, and sensual touches and kisses) does not make these two different acts the same action, just as the fact that a person taking another footstep immediately after he have taken a previous footstep does not make the two footsteps the same action.
“Lastly comes the sin of not observing the right manner of copulation, which is more grievous if the abuse regards the ‘vas’ [the vessel or the orifice of a woman] than if it affects the manner of copulation in respect of other circumstances.” (St. Thomas Aquinas, Summa Theologica, Second Part of the Second Part, Q. 154, Art. 12)
The Church teaches that any act which is intrinsically evil cannot be moral, regardless of circumstance or intention. Unnatural sex acts (such as oral, anal and manual sex) are intrinsically evil and therefore cannot become moral by being combined with, preceded by, or followed by, a moral act of natural marital relations performed for the primary purpose of begetting children. “No difficulty can arise that justifies the putting aside of the law of God which forbids all acts intrinsically evil. There is no possible circumstance in which husband and wife cannot, strengthened by the grace of God, fulfill faithfully their duties and preserve in wedlock their chastity unspotted.” (Pope Pius XI, Casti Connubii #61)
Now (in the 20th and the 21th century) there are many ‘teachers’ who are teaching the exact opposite idea, but they have no explanation for how an act that is intrinsically evil can become good by being combined with another act. As an analogy, killing an innocent person in order to steal his money is immoral, and it does not become moral by being combined with or followed by the act of donating the money to charity. “And should we not do evil, so that good may result? For so we have been slandered, and so some have claimed we said; their condemnation is just.” (Romans 3:8)
One of the greatest evidences that proves that non-procreative sexual acts are inherently sinful and that they can never be excused or justified in any circumstance is that not a single Pope or Saint in the 2000 year history of the Church ever taught that they could be done either by themselves or in relationship to the marital act but that, as we have seen, and as we will see, The Holy Bible and all Popes, Church Fathers, and Saints unanimously condemned these acts. Only in the debauched and immoral 20th century did this vile and monstrous teaching spring up from the pit of Hell, directly fulfilling biblical prophecy: “For there shall be a time, when they will not endure sound doctrine; but, according to their own desires, they will heap to themselves teachers, having itching ears.” (2 Timothy 4:3)
Unnatural sexual acts are inherently non-procreative; such acts are, by their very nature, not open to the possibility of conceiving a child.
“But no reason, however grave, may be put forward by which anything intrinsically against nature may become conformable to nature and morally good. Since, therefore, the conjugal act is destined primarily by nature for the begetting of children, those who, in exercising it, deliberately frustrate its natural power and purpose, sin against nature and commit a deed which is shameful and intrinsically vicious.” (Pope Pius XI, Casti Connubii #54)
Unnatural sexual acts are intrinsically against nature because the conjugal act is primarily directed toward procreation – the begetting of children. Those persons (married or not) who deliberately choose sexual acts deprived of the natural power and purpose of procreation “sin against nature” and commit a shameful and intrinsically evil act.
“Since, therefore, openly departing from the uninterrupted Christian tradition some recently have judged it possible solemnly to declare another doctrine [that is, a heretical and false doctrine which contradicts the Church’s constant and infallible teaching that the primary end or purpose of the marital act is the procreation of children] regarding this question, the Catholic Church, to whom God has entrusted the defense of the integrity and purity of morals, standing erect in the midst of the moral ruin which surrounds her, in order that she may preserve the chastity of the nuptial union from being defiled by this foul stain, raises her voice in token of her divine ambassadorship and through Our mouth proclaims anew: any use whatsoever of matrimony exercised in such a way that the act is deliberately frustrated in its natural power to generate life is an offense against the law of God and of nature, and those who indulge in such are branded with the guilt of a grave sin.” (Pope Pius XI, Casti Connubii #56)
This infallible teaching of the Church which says that “any use whatsoever of matrimony in such a way that the act is deliberately frustrated in its natural power to generate life is an offense against the law of God and of nature,” must be understood to condemn not only contracepted sexual acts, but also any and all non-procreative sexual acts, even within marriage, including unnatural sexual acts. For all sexual acts are a deliberate use of the sexual faculty, and all unnatural sexual acts are a deliberate choice of an act that are inherently non-procreative. If the Pope had wished to narrow his statements to only contraception, he would not have said “any use whatsoever,” or if he had wished to allow unnatural sexual acts within marriage, he would not have said “any use whatsoever of matrimony.”
Instead, he unequivocally proclaimed the Magisterium’s definitive teaching, which is also found in Holy Scripture, Sacred Tradition and the Natural Law, that each and every marital sexual act must include the procreative meaning. This teaching necessarily prohibits the married couple from engaging in any kind of unnatural sexual act (with or without climax), because all such acts lack the procreative meaning. This is also why Pope Pius XI teaches that spouses are not forbidden to consider the secondary ends of marriage “SO LONG AS THEY ARE SUBORDINATED TO THE PRIMARY END [that is, Procreation of children] and so long as the intrinsic nature of the act is preserved.”
Pope Pius XI, Casti Connubii (# 59), Dec. 31, 1930: “For in matrimony as well as in the use of the matrimonial right there are also secondary ends, such as mutual aid, the cultivating of mutual love, and the quieting of concupiscence which husband and wife are not forbidden to consider SO LONG AS THEY ARE SUBORDINATED TO THE PRIMARY END [that is, Procreation of children]and so long as the intrinsic nature of the act is preserved [that is, all sexual acts must be able to procreate in themselves, which means that no unnatural and non-procreative form of a sexual act can ever be performed without sin].”