449. That the lust of fornication is not the lust of adultery is seen by every one from common perception. What law and what judge would charge a fornicator with the same crime as an adulterer? The reason why this is seen from common perception is because fornication is not opposed to conjugial love as adultery is. In fornication, conjugial love may lie hidden within, as the spiritual in the natural. Indeed, the spiritual is actually evolved out of the natural, and when evolved, the natural surrounds it as bark surrounds a tree and a scabbard a sword. It also serves the spiritual for protection against violence. It is evident from this, that the natural love which is directed to the sex, precedes the spiritual love which is directed to one of the sex; but if fornication come from the natural love of the sex, it can also be wiped away, provided conjugial love is looked to, desired, and sought as the principal good.
The case is wholly different with the libidinous and obscene love of adultery. That this is the opponent and destroyer of conjugial love was shown in the preceding chapter on The Opposition of Scortatory Love and Conjugial Love. Therefore, if for various reasons an adulterer from purpose or confirmation enters the conjugial bed, an inversion takes place. Within lies hidden the natural with its lascivious and obscene things, and outwardly veiling it about is an appearance of the spiritual. Reason can see from the above that as compared with the lust of adultery, the lust of limited fornication is as the first mildness [of winter] to the cold of a mid-winter in northern regions.