Distinguishing Sexual Desire from Lust
There are a few objections that rise up immediately in some who hear this explanation for the first time, and it's best to introduce them right from the start.
The first objection is the assertion that the sexual buzz which develops in a mostly indiscriminate way is nothing more than natural sexual desire. In fact, most definitions of lust describe it as a normal desire that has gone astray, without explaining plainly when this occurs.
Unfortunately, there is a fundamental problem with using the term "desire" or "sexual desire" as the starting point when developing a suitable, practical definition of lust. The word "desire" conveys the idea of hope or wish for future fulfillment. In contrast, those who lust are not just thirsty—they are drinking from the cup as well.
We are constantly exposed to sexual stimulations, primarily visual. This is the world in which we live. It is natural to have a sexual reaction to such stimulation. This is because of sexual desire—a part of who we are.
We are not permitted, however, to take the next step in cases when this sexual attraction is misdirected. Some may argue that one cannot stop illicit gratification. But there's an easy way to prove that wrong: we routinely recoil from lust or sexualized interactions with family members such as daughters or sisters. Focusing our attention in order to obtain an illicit sexual buzz is willful and sinful. That quick gulp of sweet "stolen water" (Proverbs 9:17) is when we have crossed into sinful lust. We may want to minimize the adultery we are allowing in our hearts, but God does not.
There is nothing wrong with sexual desire—as long as it is not followed up with lust. It is a finely tuned and powerful God-given capacity, and we should not expect it to go away or find any fault with it. As Uncle Screwtape, the demon tutor wrote to his pupil, Wormwood, in The Screwtape Letters (C. S. Lewis):
He [God] made the pleasures: all our research so far has not enabled us to produce one. All we can do is to encourage the humans to take the pleasures which our enemy has produced, at times, or in ways or in degrees, which He has forbidden.
The issue is whether we will use our desires to engage in sin. Ramped up sexual desires are only permitted as we share and enjoy them within the marriage relationship. The sin of lust occurs when we allow ourselves illicit sexual pleasure by misusing sexual desire.
Do not believe the lie that you cannot deny yourself illicit gratification when tempted. We can—and must—whenever we are tempted to sin.
Another objection to describing lust as an illicit sexual buzz is based on the assertion that we cannot eliminate sexual thoughts. But this is not the goal for which we are striving. Certainly, taking charge of our thought lives is a critical front in the battle against lust for a Christian—"Let the wicked forsake his way, and the unrighteous man his thoughts" (Isaiah 55:7).
However, having sexual thoughts is not the same as committing lust. It is only when we improperly dwell on such thoughts to develop the recognizable experience of an illicit sexual buzz that we have sinned. In this way, the sin of lust is comparable to other sins to which we are susceptible. At times, we all face situations that provoke us to anger, but if we improperly dwell on that anger, we slip into sins such as rage, bitterness, and unforgiveness.