We often define ourselves by what we desire most. Be yourself. Fulfill your dream. I can love who I want. But it is not always right to be yourself, nor to fulfill any dream, nor even to love who you want. God cares about how you define yourself, what you dream of, and even whom you sexually desire.
In the Sermon on the Mount, Jesus makes this last point clear when he names looking after someone with lustful intent as the equivalent to adultery. Here, Jesus warns us against following certain desires. He tells us that desire can become sin.
While these words may be commonplace to many Christians, we sometimes struggle to grasp the difference between good desire and bad desire as in looking at someone with “lustful intent.” The Holy Spirit has gifted the church with many gifted teachers throughout the ages, and in particular Augustine of Hippo (354–430) was given insight into Jesus’ words here.
So below, I offer a brief overview of Jesus’ words followed by Augustine’s pastoral reflection to help us understand how our desires can turn into sin so that we can know what is good (good desires) and avoid what is not (sinful desires).
The Sermon on the Mount
In the first place, it is important to understand the context of Jesus’ words on lustful intent. When the Lord preached his Sermon on the Mount, he fulfilled the law (cf. Matt 5:17). He did so by delivering a new law (as Moses did before) and by pointing to the heart of the law.
In so doing, Jesus did not internalize the law that was supposedly external under the Old Covenant. The tenth commandment itself forbids even “desiring” something that does not belong to a person.
Instead, Jesus rightly embraces the already-internalized meaning of the law while also clarifying and giving it an expression that makes sense under the New Covenant. Put simply, the Sermon on the Mount assumes the presence of the Holy Spirit to fulfill its obligations.
The Old Covenant, while good and holy, excites sin in our bodies as Paul says (Rom 7:8, 12) and contains allowances due to human weakness as Jesus says (Matt 19:8).
The New Covenant does not make any such allowances because it assumes we can fulfill the whole law by the Holy Spirit, that is, by loving God and neighbour as ourselves.
Hence, Jesus elevates God’s law and imposes a higher standard upon his hearers because he knows that upon receiving the Holy Spirit, we can fulfill the perfect command of the law—the royal law.
In this context, Jesus explains that lustful desire is sin
When desire becomes sin
“You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart. (Matt 6:27–28)
The Lord here cites one of the ten commandments, “You shall not commit adultery” (Exod 20:14) and then speaks of the command at a more fundamental level: desire. He discerns the intent of the law rightly as the tenth commandment forbids desiring wrongly.
Yet as the law-giver who gave the law first to Moses and now delivers it himself, Jesus makes full the law of God in the Sermon on the Mount. He pinpoints sin as a certain kind of desire that leads to physical acts. Yes, adultery itself is sinful, but even lustful intent is sinful.
So what is “lustful intent” and how does it make one commit adultery? Or more generally, when does desire become sin? Augustine provides particularly helpful guidance here.
Suggestion, pleasure, and consent
Augustine observes three steps in committing sin: suggestion, pleasure, consent.* It all begins with suggestion which comes to us either through memory or sense perception. Next, comes pleasure.
Pleasure may rightly enjoy something suggested to us unless that thing is forbidden. Reason must control pleasure as when we desire food when fasting, yet we do not eat because of the fast. “Were we to yield to it,” writes Augustine, “we would commit sin surely, a sin in the heart of known to God, though actually it may remain unknown to man” (Sermon on the Mount, 1.12.34).
Augustine applies his observations on the progression of sin to Jesus’ saying about looking after someone with lustful intent. He explains, “Now, this is not merely to be tickled by the pleasure of the flesh, but it is the full consent to the pleasure: the forbidden craving is not checked, but, given the opportunity, it would gratify its desire” (1.12.33).
The idea of checking sin by reason is key for Augustine because reason should define when we consent to pleasure or do not consent to pleasure when it is, for example, forbidden pleasure (1.12.34).
Augustine understands this sequence to occur in the garden of Eden. The serpent suggests the fruit to the senses, Eve takes pleasure in her desire for the fruit, and Adam (argues Augustine) consents to the sin by reason (1.12.34).
Summarizing how consent itself makes something sinful, Augustine writes, “But to yield consent to a forbidden pleasure is a great sin; and the sin which a person commits in yielding consent is in his heart” (1.12.34).
In the above discussion, Augustine defines consent to forbidden pleasure, which memory or the senses suggest to us, as sin. He clarifies that “to be tickled by pleasure” is not yet consent and so no “great sin” and probably not even sin at all.
Likely, by tickling, he means the sort of natural recognition of someone’s attractiveness or beauty. Someone can observe a beautiful person and so have the suggestion of forbidden pleasure without consenting to it.
Elsewhere, Augustine explains:
You cannot say that your inner attitude is good if with your eyes you desire to possess a woman, for the eye is the herald of the heart. And if people allow their impure intentions to appear, albeit without words but just by looking at each other and finding pleasure in each other’s passion, even though not in each other’s arms, we cannot speak any longer of true chastity which is precisely that of the heart (The Rule of saint Augustine 4.4).
Yet reason can check the suggestion of pleasure so that we do not look after this person with “lustful intent.”
So how does desire become sin?
Augustine’s observations clarify what it means to look after someone with lustful intent (Matt 6:28). To see an attractive person may involve the suggestion of forbidden pleasure. If someone consents to that pleasure and so does not check it with reason, then sin happens.
And then a person who “looks at a woman with lustful intent” will have “committed adultery with her in his heart.”
*Unless otherwise noted, this discussion summarizes Augustine, Sermon on the Mount, 1.12.34