Lust

Lust, luxuria, is defined in the tradition as desire for sexual pleasure sought outside its proper order rather than as sexual desire itself, and both Aquinas and the Catechism of the Catholic Church are explicit that the appetite is natural and that the disorder lies in its separation from its ends. In Evagrius and Cassian the corresponding logismos is porneia, and the monastic treatment is concerned with the management of thought and imagination rather than with acts. Aquinas subdivides the vice into species and treats it, with gluttony, as one of the two vices of the flesh, which he holds to be less grave than the spiritual vices of pride and envy though often more shameful, a distinction that runs against the popular assumption that the sexual sins are the worst.

The Eastern Christian tradition never systematized the vice into the same confessional casuistry as the Latin West; instead, the eighteenth-century Philokalia, an anthology of ascetic texts compiled by Nikodemos of the Holy Mountain and Makarios of Corinth that remains central to Orthodox spiritual practice, preserves Evagrius's and Cassian's original desert vocabulary of porneia largely unchanged, treating it as a thought to be watched and refused rather than an act to be classified into species and degrees the way Western manuals of moral theology, built for use in the confessional, came to require.