445.
(1) Fornication is the product of a love for the opposite sex. We say that fornication is the product of a love for the opposite sex, because fornication is not love for the opposite sex, but stems
from it. Love for the opposite sex is like a spring from which either conjugial love or licentious love can issue; and they can issue from it through fornication and apart from fornication. For a love
for the opposite sex is present in every person, and either it ventures forth, or it does not. If it ventures forth before marriage with a fallen woman, it is called fornication. If it ventures
forth for the first time with a wife, it is called marriage. If it ventures forth after marriage with another woman, it is called adultery. Consequently, as we said, love for the opposite sex is like
a spring, from which can flow either a chaste love or an unchaste love. However, with what caution and prudence a chaste conjugial love may develop through fornication, and as a result of what imprudence
an unchaste or licentious love develops through it, will be explained in discussions that follow. Who can conclude that it is not possible for a person who has fornicated to be more chaste
in marriage?