When recounting the effects of lust on the soul, the late German philosopher Josef Pieper described its tendency to “destroy the structure of the person” by directly undermining prudence. The result of this, he argued in The Four Cardinal Virtues, is that lust “begets a blindness of spirit” which makes it almost impossible to perceive spiritual goods. Conversely, it is the virtue of chastity which “more than any other makes man capable and ready for contemplation”.
Along similar lines, St Thomas Aquinas points out in his Quaestiones Disputatae de Veritate that even an evil man is capable of delivering prophecy (think of Balaam in the Book of Numbers, or Caiaphas in the Gospel of John). The only person who is unable to prophesy is the one who is dominated by sins of the flesh. The reason for this is that sins of the flesh cloud our spiritual senses through the irrational fixation on bodily pleasures. Such pleasures are good in themselves, but when we pursue them at the expense of reason, we lose something of our humanity in the process. Instead of acting as persons, we reduce ourselves to the level of the animals.
