1. Sexual Concupiscence
Lust or carnal concupiscence can be described as the engrossing urge for pleasure and exploitative possession which, in our present condition, almost always accompanies sexual desire and tends to take it over. From the moral point of view, it is a negative force and a powerful enemy of true human and spiritual growth.
The Christian idea of sexual concupiscence can only be understood in the light of the Fall. Christians hold that the original state of man and woman vis-à-vis each other was one of joyous harmony, particularly in relation to their reciprocal sexuality with its potential for mutual appreciation and enrichment, and for unitive and fruitful love. The mutual attraction between man and woman naturally has its physical aspect and this too, as the Catechism says, is part of "the Creator's own gift" (1607).
Sin wrecked this easy and harmonious peace of the man-woman relationship. After the Fall, says the Catechism, "the harmony in which they [Adam and Eve] had found themselves, thanks to original justice, is now destroyed: the control of the soul's spiritual faculties over the body is shattered" (400); and this disorder can extend to the marital relationship itself: "the union of man and woman becomes subject to tensions, their relations henceforth marked by lust and domination" (ibid.; cf. 409).