Catholic Encyclopedia (1913)/Incest
(Latin. in, not, and castus, chaste).
Incest is sexual intercourse between those who are related by blood or marriage. Its specific malice is contracted by such unlawful commerce between those related within the fourth degree of consanguinity or affinity, as computed by canonists. The guilt is incurred not only by those sinful acts which are, as theologians say, fully consummated, but also by incomplete acts. The particular deformity of incest comes not merely from the violation of the virtue of chastity, but also from the offence against the mingled affection and reverence with which parents and, proportionately, other relatives should be regarded. It is certain that this crime has its distinctive enormity from the prohibition of the natural law, where there is question of the first degree in the direct line, for instance, between parents and children. For the other degrees it is probable that recourse must be had to the ecclesiastical law which invalidates marriage within those limits. It is commonly held, with regard to those related by consanguinity or affinity, that with the exception of the first degree in the direct line all forms of incest are, morally speaking, of the same species, and therefore for the integrity of confession there is no necessity to distinguish between them. It must be noted, however, that carnal sins between those who are spiritually or legally related within the degrees that would render their marriage invalid, are separate species of incest. A decree of the Holy Office, 25 June, 1885, declares that in applications for matrimonial dispensations it is no longer necessary to make mention of the circumstance of incestuous relations between the petitioners.
JOSEPH F. DELANY