The Catechism of the Catholic Church states that purity of heart consists in three things: “charity; chastity or sexual rectitude; love of truth and orthodoxy of faith.” The idea is that a power becomes impure by being exercised on the wrong object and pure by being exercised on its proper object. The mind of a human being is purified by knowledge and love of truth, and the will by love of the good. “Chastity or sexual rectitude” refers to the sensitive appetite, but why this area in particular, rather than temperance in general? The reason for this is that the appetite for sexual pleasure is among the strongest in man and therefore among the most likely to lead him against reason. Thus we see that many reject all possible restrictions on sexual desires, saying that everything is licit as long as one does not harm others, even though in any other area this would be obviously absurd: thus no one thinks it is virtuous to give oneself to eating and drinking without any restraint whatsoever, as long as one doesn’t harm others. In relation to the sensitive appetite, therefore, purity of heart most of all requires purity in regard to sexual desires. Nonetheless, one cannot wholly exclude other sensitive desires from purity of heart.