448.  IV.  FORNICATION IS LUST, BUT NOT THE LUST OF ADULTERY.  The reasons why fornication is lust are, 1.  Because it proceeds from the natural man, and in everything which proceeds from the natural man, there is concupiscence and lust; for the natural man is nothing but an abode and receptacle of concupiscences and lust, since all the criminal propensities inherited from the parents reside therein. 2.  Because the fornicator has a vague and promiscuous regard to the sex, and does not as yet confine his attention to one of the sex; and so long as he is in this state, he is prompted by lust to do what he does; but in proportion as he confines his attention to one of the sex, and loves to conjoin his life with hers, concupiscence becomes a chaste affection, and lust becomes human love.

449.  That the lust of fornication is not the lust of adultery, every one sees clearly from common perception.  What law and what judge imputes a like criminality to the fornicator as to the 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 stored up within, as what is spiritual may lie stored up in what is natural; yea, what is spiritual is also actually disengaged from what is natural; and when the spiritual is disengaged, then the natural encompasses it, as bark does its wood, and a scabbard its sword, and also serves the spiritual as a defence against violence.  From these considerations it is evident, that natural love, which is love to the sex, precedes spiritual love which is love to one of the sex; but if fornication comes into effect from the natural love of the sex, it may also be wiped away, provided conjugial love be regarded, desired, and sought, as the chief good.  It is altogether otherwise with the libidinous and obscene love of adultery, which we have shewn to be opposite to conjugial love, and destructive thereof, in the foregoing chapter concerning the opposition of adulterous and conjugial love:  wherefore if a confirmed and determined adulterer for various reasons enters into a conjugial engagement, the above case is inverted, since a natural principle lies concealed within its lascivious and obscene things, and a spiritual appearance covers it externally.  From these considerations reason may see, that the lust of limited fornication is, in respect to the lust of adultery, as the first warmth is to the cold of mid-winter in northern countries.

450.  V. WITH SOME MEN THE LOVE OF THE SEX CANNOT WITHOUT HURT BE TOTALLY CHECKED FROM GOING FORTH INTO FORNICATION.  It is needless to recount the mischiefs which may be caused and produced by too great a check of the love of the sex, with such persons as labor under a superabundant venereal heat; from this source are to be traced the origins of certain diseases of the body and distempers of the mind, not to mention unknown evils, which are not to be named; it is otherwise