About sexual thoughts and fantasies inside and outside of the marital act
It is of the Divine law that a person may never willfully entertain sexual thoughts in his mind, even about his wife, outside of the marital act. The only sexual act the Church allows is the normal, natural, and procreative marital act. Everything else is contrary to the only primary end or intent of the sexual act—the procreation of children. If a person willfully entertains sexual thoughts outside of the marital act or unnecessarily puts himself into sexual temptations when there is no need to, he or she commits a mortal sin. Consequently, one may not even entertain or consent to sexual thoughts about one’s own wife or husband outside of the marital act, but must resist these thoughts or temptations as one would resist the thought of adultery or fornication: “Several doctors [of Divinity] maintain that willingly fostering wicked carnal thoughts in order to enjoy oneself is a deadly sin, even without doing the deed. Be sure, however, that kisses, gazes, and fondling, mainly caused by such wicked and lustful thoughts, without anything more, is an even greater sin. … it is even worse if these kisses do not respect the honesty which is usually kept in public.” (Jean Gerson, Oeuvres Complétes)
Simply said, women or men are not toys, playthings, or “bunnies” from which to derive sexual stimulation. When women or even one’s own wife are used in sexual fantasies, they are sexually abused, even if they are untouched. Many men rape many women each day and commit adultery, fornication and illicit sexual acts without laying a hand on them. Women also rape men and commit adultery, fornication and illicit sexual acts in this way. These rapes, fornications, illicit sexual acts and adulteries are not marked by physical violence but by psychological warfare. Because a person is often unaware of being used and abused, and because the abuser often does not fathom the real extent of the severity of his crime, this makes these mental and visual rapes/abuses/sexual crimes seem less devastating. Nevertheless, grave sin with all its degradation and death is being committed.
For instance, it would be quite sick for a husband not to resist sexual thoughts about his wife or to continually entertain such thoughts while at work or while on a trip, because while at work or while on a trip there is no chance for him to lawfully quiet his concupiscence and perform the marital act for procreational purposes. That’s why dwelling on such thoughts only would distract him spiritually and temporally and could even lead him into committing other sins, such as masturbation or adultery (in thought as well as in deed). All who do not wish to be damned must thus resist sexual thoughts and temptations outside of the marital act and may not entertain them in anyway.
It is of course one thing to be tempted to have sexual relations with one’s own wife or someone else (which is not sinful) and a whole other thing to consent to having sex with them in one’s thought or mind (which is sinful). Thus, a husband and wife may never consent to any sexual thoughts or fantasies about their spouse outside of the normal and natural marital act. However, that is not to say that it’s licit to think about bad or illicit things or give consent to them during the marital act—as so many evil and heretical people and so-called theologians actually teach today—for that is not what it means. What it means is simply that a person can only fully consent to, and give way to, sexual thoughts and desires (about their spouse) during the sexual act without committing any sin, so long as these thoughts range within what is lawful, natural, reasonable and necessary for the completion of the marital act to occur.
St. Thomas Aquinas wonderfully explains this thought process further to us in his Summa:
“Accordingly a man who is thinking of fornication, may delight in either of two things: first, in the thought itself [by merely thinking about it but not necessarily giving consent to it or the pleasure derived from it], secondly, in the fornication thought of. Now the delectation [pleasure] in the thought itself results from the inclination of the appetite to the thought; and the thought itself is not in itself a mortal sin; sometimes indeed it is only a venial sin, as when a man thinks of such a thing for no purpose; and sometimes it is no sin at all, as when a man has a purpose in thinking of it; for instance, he may wish to preach or dispute about it. Consequently such affection or delectation [pleasure] in respect of the thought of fornication is not a mortal sin in virtue of its genus, but is sometimes a venial sin and sometimes no sin at all: wherefore neither is it a mortal sin to consent to such a thought [it only becomes a mortal sin if one consents to and wants to have the illicit pleasure in the thought]. In this sense the first opinion is true. But that a man in thinking of fornication [or other unreasonable or sinful sexual acts] takes pleasure in the act thought of, is due to his desire being inclined to this act. Wherefore the fact that a man consents to such a delectation [pleasure], amounts to nothing less than a consent to the inclination of his appetite to fornication [or other sinful sexual acts]: for no man takes pleasure except in that which is in conformity with his appetite. Now it is a mortal sin, if a man deliberately chooses that his appetite be conformed to what is in itself a mortal sin. Wherefore such a consent to delectation [or pleasure] in a mortal sin, is itself a mortal sin, as the second opinion maintains.” (St. Thomas Aquinas, Summa Theologica, First Part of the Second Part, Q 74, Art. 8)
Thus, if even pleasurable sexual thoughts outside of the marital act of one’s own legitimate spouse is sinful if not fought against, how much more must not the sensual thoughts of one’s neighbor be? If even kisses between married spouses for the purpose of carnal pleasure is condemned as a mortal sin by the Catholic Church, how much more must not the perversions of the marital acts be that so many spouses today practice?
St. Augustine, On the Morals of the Catholic Church, Chapter 30, Section 62, A.D. 388: “For to Christians this rule of life is given, that we should love the Lord Our God with all the heart, with all the soul, and with all the mind, and our neighbor as ourselves... God alone, to find whom is the happiest life, must be worshiped in perfect purity and chastity... in chaste and faithful obedience, not to gratify passion, but for the propagation of offspring, and for domestic society.”