The word lust is most often used to refer to excessive or disordered sexual desire. However, because it is rooted in the Latin word luxuria (which refers to extravagant, excessive, or even riotous behavior), we sometimes hear it used in other ways. For example, someone may be said to have a “lust for power.” In the realm of moral and spiritual theology, though, we have come to restrict the word to sexual matters. This is especially because we have specific words to describe such excesses gluttony and greed.

Lust defined - For our discussion here we will define lust as disordered desire for, or inordinate enjoyment of, sexual pleasure (see Catechism of the Catholic Church 2351).

Of itself sexual desire is a great good, and an essential one upon which depends the future existence of the human race. As such it is also related to the common good and is among the greatest of goods since human life comes from it.

It is for this reason that St. Thomas numbers lust (objectively speaking) among the mortal sins:

The more necessary a thing is, the more it behooves one to observe the order of reason in its regard; wherefore the more sinful it becomes if the order of reason be forsaken. Now the use of venereal acts, as stated in the foregoing Article, is most necessary for the common good, namely the preservation of the human race. Wherefore there is the greatest necessity for observing the order of reason in this matter: so that if anything be done in this connection against the dictate of reason's ordering, it will be a sin. Now lust consists essentially in exceeding the order and mode of reason in the matter of venereal acts. Wherefore without any doubt lust is a sin (Summa Theologiae II, IIae 153.3).

But lust is either an inordinate desire or a disordered one (often both). To say that sexual desire is disordered means that it is not directed to its proper purpose or end. The Catechism says, Sexual pleasure is morally disordered when sought for itself, isolated from its procreative and unitive purposes (CCC 2351). To say that it is inordinate is to say that it is excessive, that the desire for sexual pleasure is over-the-top; it becomes a distracting, even consuming thing. This usually results from overindulging sexual desire and it can set forth an addictive process in which more and more sexual pleasure is “needed” to cool its flames. On this level, lust can become destructive to an individual, to others, and to a society as a whole.

In our time it is difficult to underestimate the harm caused by the widespread tolerance and celebration of lust and promiscuity. The acceptance of pre-marital sex (fornication), cohabitation, abortion, and pornography has led to sexually transmitted diseases, AIDS, the sexualizing of children, single motherhood, absentee fathers, teenage pregnancy, sexual confusion, divorce, and finally the incalculable harm caused by the fact that more than half of children in the United States are not raised in normal family settings. As is common with adult misbehavior, it is the children who pay the highest price.

The most fundamental damage that widespread promiscuity has caused is the destruction of marriage and the family. Marriage rates have dropped dramatically in the Western world with the outright celebration of lust in music, movies, popular culture, and pornography. The widespread promotion of contraception has also perpetrated the lie that there can be sex without consequences.

As a result of this widespread promiscuity and uncontrolled lust many families are in disarray due to divorce, remarriage, single motherhood and absent and passive fathers. Because marriage and the family form the foundation of culture and civilization, our current path is a civilization-killer. Yet very few today seem to have a mind clear enough to recognize the path we are on and to repent.

St. Thomas provides a clue as to why this is so and also describes an additional harm caused by lust: the loss of a clear mind. He writes,

Now carnal vices, namely gluttony and lust, are concerned with pleasures of touch in matters of food and sex; and these are the most impetuous of all pleasures of the body. For this reason, these vices cause man's attention to be very firmly fixed on corporeal things … [As a] consequence man’s operation in regard to intelligible (obvious) things is weakened,

[This is caused] more, however, by lust than by gluttony, forasmuch as sexual pleasures are more vehement than those of the table. Wherefore lust gives rise to blindness of mind, which excludes almost entirely the knowledge of spiritual things, while dullness of sense arises from gluttony, which makes a man weak in regard to the same intelligible things. 

On the other hand, the contrary virtues, viz. abstinence and chastity, dispose man very much to the perfection of intellectual operation. Hence it is written (Daniel 1:17) that “to these children” on account of their abstinence and continency, “God gave knowledge and understanding in every book, and wisdom” (Summa Theologiae II, IIae 15.3).

Yes, along with indulged lust comes a darkening of the intellect. St. Paul notes the same thing: 

The wrath of God is being revealed from heaven against all the godlessness and wickedness of men who suppress the truth by their wickedness … they became futile in their thinking and their senseless minds were darkened. Although they claimed to be wise, they became fools…God gave them up in the desires of their hearts to impurity for the dishonoring of their bodies with one another. They exchanged the truth of God for a lie … for this reason God gave them over to dishonorable passions. Their women exchanged natural relations for unnatural ones. Likewise, the men abandoned natural relations with women and burned with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their error (Romans 1:18ff).

In our times a darkening of the intellect has come upon many, who cannot and will not see that widespread promiscuity has caused great harm and threatens our very future as a culture and civilization.

St. Thomas also enumerates the following “daughters” of lust: darkness of mind, thoughtlessness, inconstancy, rashness, self-love, hatred of God, love of this world, and abhorrence or despair of a future world. St Paul well describes the darkness of mind that comes from suppressing the truth about sexuality (cf Rom 1:17ff). As one’s mind grow darker, strange practices once thought shameful are approved. One also becomes thoughtless by denying consequences of unreasonable and sinful use of the sexual faculties, one is also thoughtless in how they treat other people and the children born from illicit sexual unions. Behaviors become increasingly rash and only the pleasures of this world are sought. Finally one comes to treat God and the Church as an enemy for daring to suggest that illicit sexual union is sinful. 

Of the Virtues that are Medicine for Lust – Clearly temperance, continence, and chastity are the key virtues. But justice also demands that we respect the prerogatives of the marriage bed (cf Heb 13:4). Piety, namely family love, also helps, so that the sexual bond is kept safe to strengthen the family. Shamefacedness, sobriety, modesty and self-control are all recommendable as well. Respect and reverence for God and neighbor are also of assistance. 

I would like to finish this reflection on lust with the paradoxical conclusion that while it is often regarded as less serious than sins against the spirit (even by traditional theologians), lust is capable of causing some of the greatest harm because it drives us downward into the flesh such that the light of reason is dimmed and the very light of truth seems obnoxious and intolerable.

Sexual desire is a beautiful gift of God and is necessary for our survival, but the corruption of the best things is the worst thing. It is far worse to damage a precious work of art than an ordinary trinket. Damaging the beautiful gift of sexual desire and longing for intimacy also damages the precious gifts of marriage and family, the basic unit of civilization. To divide what God has united (sex and marriage, marriage and children, husband and wife) is a kind of nuclear fission that has enormous destructive potential. Only the “control rods” of chastity and purity can contain the destruction we have set loose. Only a recommittal to not separating what God has joined can end the inevitable destruction caused by unrestrained lust.