The Capital Sins: “Lust”

By Father Reginald Martin, O.P.


Several years ago, when we considered the Sixth Commandment, we observed that human sexuality is an immense blessing, one that comes with the correspondingly high price of our human responsibility. The first act of this responsibility is to remember that man and woman are equally created in God’s image. Therefore, the Catechism observes, quoting Pope St. John Paul II, “God gives man and woman an equal personal dignity.” (CCC, # 2334) This dignity is realized most visibly and completely in Christian marriage. The old admonition read to couples at their wedding ceremony reminded them that in the Sacrament of Matrimony, God

…gave to man a share in the greatest work of creation, the work of the continuation of the human race. And in this way he sanctified human love and enabled man and woman to help each other live as children of God, by sharing a common life under his fatherly care.


The words of this admonition are an elegant summary of the Church’s teaching on the proper use of our human sexuality. And as we embark upon the sad task of considering the sin of lust, we will find ourselves repeatedly contrasting this sin to the virtuous example of enjoying the gift of human sexuality within the context of marriage.


St. Thomas Aquinas ordinarily provides definitions that are quite detailed and require serious study if we are fully to grasp them. When he addresses lust, however, the Angelic Doctor sets a standard for simplicity, observing only

Venereal [sexual] pleasures above all debauch a man’s mind. Therefore lust is especially concerned with such like pleasures. (ST II-II, 153.1)


He continues, “A sin, in human acts, is that which is against the order of reason,” and adds, “…the order of reason consists in its ordering everything to its end in a fitting manner.” (ST II-II, 153.2) These words are key to understanding the sin of lust: it is a misuse of our human sexuality, the pleasure of which is designed to draw married partners closer together, and to guarantee the future of our human race.

No one will question the seriousness of continuing the human race. The necessity of providing for our future helps us understand the importance of our sexuality – and grasp the seriousness of its misuse. Here again, St. Thomas offers a wise reflection,

The more necessary a thing is, the more it behooves one to observe the order of reason in its regard; [likewise] the more sinful it becomes if the order of reason be forsaken. (ST II-II, 153.3)


Lust is a serious sin because it turns us away from the true goals for which we have been given the gift of our sexuality. However, because the physical pleasures promised by lust are so great, lust can intrude in our lives by confusing our higher, mental and spiritual faculties – our reason and our will – as well.


When he considers the havoc lust can wreak in our Christian life, St. Thomas cites rashness, which is a lack of moderation or control. So, too, is thoughtlessness, which affects our capacity to judge between right and wrong, and inconstancy, which is an inability to remain faithful to our commitments.

The effects of lust on our will are twofold, and both involve lust’s tempting us to choose ourselves, and what we perceive as our immediate, personal good, over the immense (but invisible) benefits God promises in the future. The first of these effects is a confusion of proper ends, namely, self-love which can become so great it results in a hatred of God because He forbids a pleasure we so ardently desire.

The second is a confusion of the things directed to their proper end. This results in a love of this world, and despair of a future world. This is not the sin of despair, by which we believe we cannot be saved, but rather so thorough-going a commitment to our sexual pleasures that we lose interest in the good things God promises in the future.


Here, perhaps, we find a clue to the overwhelming presence of sex in our society. We need consider almost any advertisement we see these days; nearly all promise what sociologists have named “instant gratification.” We may identify the flaws in this promise, but we cannot deny its appeal. Nor can we deny that God’s promises may sometimes pale in comparison. In the middle of the last century, a Dominican theologian, Thomas Gilby, summed up modern humanity’s moral plight when he wrote, “Man cannot live without joy. That is why one deprived of spiritual joy goes over to carnal pleasures.” (Peter Kreeft, Practical Theology, Spiritual Direction from Saint Thomas Aquinas, p. 188.)


When we began this reflection we observed that our human sexuality realizes its highest goal in Christian marriage. We should not be surprised, then, to learn that the sins of lust increase in gravity as they less and less mirror the sexual union of married couples. Fornication, or sexual relations between a man and woman unmarried to one another, may duplicate the sexual activity of husband and wife, but their union is not intended to foster the couple’s common life as partners in marriage. Moreover, although the sexual acts of unmarried partners may produce children, these children will be deprived of the benefits that come from a true marriage.


We might be surprised to learn that when he considers the sinfulness of fornication, St. Thomas identifies the penalty suffered by children born to unmarried parents the primary ill attached to the act. He states, “…every sin committed directly against human life is a mortal sin,” and adds

Now it is evident that the upbringing of a human child requires not only the mother’s care for his nourishment, but much more the care of a father as guide and guardian…Hence human nature rebels against an indeterminate union of the sexes and demands that a man should be united to a determinate woman…since fornication is an indeterminate union of the sexes… it is opposed to the good of the child’s upbringing…. (ST. II-II, 154.2)


St. Thomas proposes a similar reason to explain the sinfulness of adultery. In addition to their obvious turning away from chastity, the adulterous individuals abandon their responsibility to foster mutual love and produce children in their own marriages, and also impede their partners’ fulfilling that same responsibility.


As we have seen, the particular characteristics of lust may be distinguished by the different conditions of the individuals who misuse their sexuality. In this regard we must consider seduction, in which a man beguiles a virgin into sacrificing her purity, and incest, in which a couple, who are members of the same family, share sexual relations. The Fourth Commandment admonishes us to honor our parents. St. Thomas teaches that the honor due parents must also be paid to “other blood relations who are descended in near degree from the same parents.” (ST II-II, 154.9)


St. Thomas defines rape narrowly, saying it is “employ[ing] force in order unlawfully to violate a virgin.” Our present-day sensibilities expand this definition, and our Catechism defines rape, simply, as “the forcible violation of the sexual intimacy of another person.” The text continues, “Rape deeply wounds the respect, freedom, and physical and moral integrity to which every person has a right.” (CCC, #2356)


Masturbation is a further example of the lustful misuse of our sexuality. This should come as no surprise, as masturbation is clearly an individual’s using for his or her own pleasure a gift designed to be shared with another, within a particular context, and for a particular reason.


Homosexual relations are an example of sexuality similarly misused. The Catechism teaches, “They close the sexual act to the gift of life. They do not proceed from a genuine affective and sexual complementarity.” (CCC, #2357)


Here we must distinguish between the act and the person who performs it. A homosexual act, or any sexual act not intended to promote family life and the holiness of marriage, is disordered. However, our Catechism observes

The number of men and women who have deep-seated homosexual tendencies is not negligible. This inclination, which is objectively disordered, constitutes for most of them a trial. They must be accepted with respect, compassion, and sensitivity. Every sign of unjust discrimination in their regard should be avoided. These persons are called to fulfill God’s will in their lives and, if they are Christians, to unite to the sacrifice of the Lord’s Cross the difficulties they may encounter from their condition. (CCC, #2358)


We earlier quoted Thomas Gilby, who wrote that our failure to find spiritual joy may lead to our choosing physical pleasure. Thomas Aquinas defines joy as the satisfaction arising from accomplishing some good work or possessing some good thing. This suggests a deepening of our spiritual life as a remedy for lust. The early Church writers realized we cannot defeat sin by our human reason alone; we must turn to God. Kevin Vost, a spiritual writer we have mentioned in earlier reflections, says the Sacrament of reconciliation is an important first step in our battle against lust and the quest for joy.


If lust continues to prompt unwholesome thoughts, Vost urges us

…immediately [to] seek God’s help, perhaps by a prayer that is very swift and powerful, such as the ancient Jesus Prayer that the Desert Fathers were so fond of: “Lord Jesus Christ, have mercy on me, a sinner.” Hereby, we immediately call out for Christ’s help to cast out the demon of fornication… [for] Christ can cast out all demons and sins…. ((Vost, The Seven Deadly Sins, p. 165)


The Litany of the Blessed Virgin addresses Mary as “Virgin most pure” and “Cause of our Joy.” Mary is our model in all things, and at every moment of our life. To address Mary by these titles, followed by the petition, “Pray for us,” identifies us with Our Blessed Mother. Together with the Rosary, these short prayers sow seeds of devotion that our faith assures us will yield the harvest of everlasting life.

Stay In Touch

Subscribe to our e-newsletter for the latest from the Confraternity