§ 5. On Incest

783. Definition. Incest is concubitus with a person joined by kinship or affinity, within the degrees in which it is not licit to enter matrimony. Moreover the malice of this sin is contracted not only by natural congress, but also by sins of lust against nature, or non-consummated sins.

Division. Since a threefold kinship is given, namely natural, spiritual, and legal, and since besides kinship affinity is also given, hence a fourfold incest is distinguished, namely: 1. incest with a blood relative up to the fourth degree; - 2. with an affine up to the fourth degree, if the affinity comes from licit copulation, and up to the second, if from illicit; 3. with a spiritual relative (which kinship arises from baptism or confirmation); - 4. with a legal relative (which kinship comes from adoption). Cf. n. 2015 ff.

784. Principles. I. Incest is a special sin, having most grave malice. For it is opposed both to chastity, and to piety and reverence owed to relatives and affines. Hence in Leviticus (20, 14 ff.) it is punished with the penalty of death; and Blessed Paul (1 Cor., 5, 1-5) gravely rebukes the incestuous man, handing him over to Satan, that he may be corrected.

785. II. Incests between spiritual and legal relatives differ in species both from one another, and from incest with blood relatives and affines; but incest between affines more probably does not differ in species from incest between blood relatives. The reason for the first is that the diverse kinships have their origin from formally diverse roots, namely: natural kinship from nature, spiritual kinship from a sacrament, legal kinship from law. Indeed, according to St. Thomas (2.2, q. 154, a. 9 and 10, ad 2), through copulation between spiritual relatives sacrilege is committed in the mode of incest. Hence this quality of incest is to be disclosed in confession. The reason for the second is that it is material whether the conjunction arises from blood or from marriage, since copulation with blood relatives and with affines is prohibited from the same motive of piety.

The opinion, indeed, that teaches these incests specifically to differ, is also probable; and the reason is that the conjunction of blood relatives arises from an intrinsic bond, i.e. from identity of the same blood received through generation; but the conjunction of affines draws its origin from an extrinsic bond, i.e. from copulation had with their blood relatives (III, 448-450; VI, 469). But in practice, this circumstance or distinction (for example, that someone sinned so many times with a sister-in-law, and so many times with his own sister) can be kept back before the confessor.

786. It is asked. Whether incests differ in species according to diversity of degrees?

Resp. 1. Incest between blood relatives of the direct line, in the first degree, differs in species from the others according to the common opinion of the Doctors; because this nearness of blood-relationship by natural law so dirimently impedes matrimony that the Church herself cannot dispense. Besides, incest committed in this degree injures piety of itself and properly, while, in other degrees, this happens only by participation.

Hence, in confession it is to be explained if a father has sinned with a daughter, or a son with his mother: which crime has a diverse malice by reason of the special reverence owed to a parent. In the same way, incest between a stepson and stepmother, and between father-in-law and daughter-in-law, mother-in-law and son-in-law, differ in species from incest between other affines (VI, 469, 470; H. Ap., IX, 17; Lehmkuhl, I, 1050).

Note. Recent authors indeed call probable the contrary opinion, which denies that incest in the first degree, between blood relatives or affines of the direct line, differs in species from other degrees. Thus Noldin, Genicot, Ballerini, and among the ancients Sporer, Suarez, Tamburini. But our opinion (which among the ancients was more common) is defended by Lugo, Cajetan, Salmant., Roncaglia, and weighty reason supports it. Cf. n. 63, 2, and 65. - See Berardi, II, n. 830, who follows St. Alphonsus.

2. It is disputed whether incest between blood relatives, in the first degree of the transverse line, namely between brother and sister, differs in species from the others. Some probably affirm, because the Church, with the law of nature apparently resisting, never dispenses in this degree. Others probably deny, because the prohibition of the Church does not seem to import any difference, and matrimony between brothers and sisters, children of Adam, was licit (VI, 470; H. Ap., IX, 18; cf. St. Thom., 2.2, q. 154, a. 9, ad 3).

As regards the other degrees of blood-relationship, according to the more probable opinion, incest does not differ in species, just as neither does it as regards the diverse degrees of affinity and legal kinship. The reason is that among them matrimony is prohibited only by positive law (ibid.).

Hence, for practice, you will conclude: a) Outside the first degree in the direct line, whether of blood-relationship or of affinity, the circumstance of degree, although it notably aggravates the sin, is not necessarily to be confessed.

b) Relatives, having obtained a dispensation for matrimony, probably do not commit incest if they fornicate before matrimony. The reason is that the dispensation takes away the prohibition of matrimony; but where matrimony is not prohibited, there is no incest (III, 452; IV, 1140). Cf. n. 2052.

c) A confessor more probably does not commit incest by having relations with his female penitent, since between them no spiritual kinship exists. But a pastor sinning with his female parishioner sins against justice, since by force of his office he is held to feed his sheep by word and example (III, 451). Several say the same of a guardian toward a ward, and of all those to whom care of minors has been specially committed. More probably otherwise, if a master sins with a maidservant, or a believer with an unbeliever, although the sin is graver. Cf. Porpora, V, 285.

The rest, as regards penalties, etc., will be explained in the treatise on Matrimony.