(e) Its third species is real sacrilege, and it occurs when impurity is committed in such a way as to show formal disrespect to a sacred object (2311). Hence, there is sacrilege of this kind when one commits impurity immediately after Communion, or when one uses the Sacrament of Penance as a means to solicit impurity. But the fact that a person commits impurity while wearing a scapular is not sacrilegious, unless contempt for the scapular was intended.
2534. Unnatural Lust.—Worst among the sins of impurity, as such, are crimes of unnatural lust, for they exercise the sexual act, not only illicitly, but also in a manner that defeats its purpose of reproduction. In some non-venereal respects, however, natural sins of impurity may be worse than the unnatural; for example, adultery is worse as regards injustice, sacrilegious lust as regards irreligion, etc. There are four distinct species of unnatural impurities— pollution, unnatural coition, sodomy, bestiality (see Denzinger, n. 1124).
(a) For procreation nature requires copulation, and hence pollution is unnatural, for it exercises semination without copulation, either alone (self-abuse, solitary vice, masturbation) or with another (softness).
(b) For procreation nature requires proper copulation, that is, one that will permit of a fertile union between the two life elements, the sperma and the ovum. Hence, unnatural coition does not comply with this necessity, for it does not employ the proper organ of sexual union, substituting rectal for vaginal intercourse, or else by some form of natural or artificial onanism it frustrates the act of its destined conclusion. This sin is worse than pollution, since pollution omits to use intercourse, whereas unnatural coition positively abuses it.
(c) For procreation nature requires heterosexual intercourse, a condition disregarded by sodomy, which is the lustful commerce of male with male (pederasty, uranism), or of female with female (tribadism, sapphism, Lesbian love). This sin is worse than unnatural coition, for it is a greater perversity to neglect one of the two needed life elements than to neglect the right process for their union (see Gen., xix. 24, 25; Lev., xx. 13; Rom., i. 26, 27).
(d) Finally, for procreation nature requires homogeneous intercourse, a law violated by bestiality, which is coition of a human being, male or female, with a brute animal. This is the worst of unnatural impurities, since it sins against the most fundamental condition for the sexual act, namely, that the participants be of the same nature (see Lev., xx. 15, 16). Similar to bestiality is the crime of necrophilism (intercourse with a corpse).
2535. Pollution.—Pollution is the voluntary emission of semen apart from coition.
(a) It is an emission, that is an external discharge. The internal secretion in the so-called female semination is also included by many under the head of pollution. The carnal motions spoken of in 2497 b are a preparation for pollution.
(b) It is a discharge of semen, that is, of the male fluid that fertilizes the female ovum. But equivalent pollution, from the moral viewpoint, is found in the discharge of certain non-prolific fluids that are accessory to generation or that produce in their movement a venereal satisfaction, such as the vaginal fluid in females (female semination), the urethral fluid in males capable or incapable of procreation (distillation). There is no pollution, however, in natural discharges such as menstruation and urination.
(c) It is apart from coition, and thus it differs from other consummated sins. But pollution may be committed either alone (solitary vice), or with another, and in the latter case it pertains reductively to adultery, fornication, sodomy, etc., as the case may be.