424. (1) The nature of licentious love is not known unless the nature of conjugial love is known. By licentious love we mean a love of adultery that destroys conjugial love, as explained above in no. 423. As for the statement that the nature of licentious love is not known unless the nature of conjugial love is known, this does not need to be demonstrated, but may simply be illustrated by comparable parallels. Who can know, for instance, what evil and falsity are, unless he knows what is good and true? Who can know what is unchaste, dishonorable, unbecoming, and ugly, unless he knows what is chaste, honorable, becoming, and beautiful? Who can discern insanities except one who is wise, or who knows what wisdom is? Or who can accurately detect dissonant discords except one who by instruction and practice has learned harmonic patterns? Similarly, who can see clearly the nature of adultery, unless he has seen clearly the nature of marriage? And who can display to his judgment the filthiness of the pleasures of licentious love, unless he has first displayed to his judgment the cleanness of conjugial love? Now, because I have completed Part One, Delights of Wisdom Relating to Conjugial Love, from the intelligence thus acquired I am able to describe Pleasures Relating to Licentious Love.