A) Lust, Normal [Simple] Sexual Desire, and Conjugal Desire
Fine distinctions need to be drawn here; to begin with, between lust and 'normal' sexual desire. This may provoke the reaction: but surely 'normal sexual desire' is inseparable from some element of lust? The objection itself points to the need for deeper analyses of sexuality, sexual reaction, and sexual attraction.
The concept of 'normal' bears reference not first to frequency but to order. Civil disorder may be frequent in certain situations, but only an improper use of language would classify it as normal. In most intersex relations concupiscent lust is just below the surface, present and ready to assert itself. Its constant presence suggests a disorder and indicates in fact a state of abnormality.
The modern difficulty in understanding the Church's teaching on married sexuality stems in large part from a failure to distinguish between lust and what is (or should be) normal sexual desire: that is, between assertive and unregulated sexual desire, bent foremost on physical self-satisfaction, and simple sexual attraction, which can include a desire for union and is characterized by respect and regulated by love. The two are not to be equated. Pope John Paul II insists on the distinction: "the perennial call ... and, in a certain sense, the perennial mutual attraction on man's part to femininity and on woman's part to masculinity, is an indirect invitation of the body. But it is not lust in the sense of the word in Matthew 5:27-28" (Theology of the Body, 148).
Lust or sexual concupiscence is a disorder and hence always an evil. Sexual desire (just as sexual pleasure) is not an evil but a good, provided it is directed and subordinated to conjugal love and made a proper part of it. Sexual desire is part of conjugal love; concupiscence, though present also in marriage, is not. Hence their moral evaluation is totally different. The distinction should be evident, but only if one carefully ponders and respects the propriety of terms.[69]