From the Fourth Lateran Council under Innocent III, A.D. 1215

Decree L. Since the prohibitions concerning marriage not at all to be contracted in the second and third genus of affinity, and concerning offspring received from second nuptials not to be coupled to the cognation of the prior husband, both frequently introduce difficulty and sometimes give birth to peril of souls, so that when the prohibition ceases the effect may cease, by the approval of the sacred council revoking the constitutions issued on this matter, by the present constitution we decree that those contracting thus henceforth be coupled freely.

Peter of Blois, in a letter given about A.D. 1180, On the Genera of Affinity, said: "There are found canons from the understanding of which scholastic industry has explained a triple genus of affinity and, in them, the distinction of diverse degrees. But according to the judgment of my conscience, this new invention and magisterial tradition does not prejudice marriage, for which the divine law prescribes certain limits." Perhaps, as Guscanvillaeus notes, Blois thought that the canons by which marriages among affines in the second and third genus were prohibited had indeed prohibited them from being made, but had not invalidated those contracted. Papinian also judged that marriages are prohibited on account of affinity exceeding the first genus (Digest, Book XXIII, Title 2, n. 15), saying: "that the former wife of a stepson ought not to be joined in marriage to the stepfather, nor ought the stepmother of him who was the husband of a stepdaughter to enter into marriage." Namely, the daughter-in-law of the wife was in the place of a daughter-in-law to the husband, and the son-in-law of the husband was in the place of a son-in-law to the wife.

Gratian, in his Concordia of Discordant Canons, cause XXXV, questions 2 and 3, had brought forward certain canons on this matter ascribed to the ancient Roman Pontiffs, whose in fact they are not. For the third canon, attributed by Gratian to Pope Fabian, is, as the correctors admonish, of Theodore of Canterbury, in whose Penitential it stands as chapter XI. But Theodore speaks of an entirely different matter; and that is what we brought forward from him under the responses of Gregory the Great. Another canon, the twelfth in the same place, ascribed by Gratian to Pope Julius, is of the same Theodore in the same place, if we believe the correctors, although in Petit's edition it does not occur in expressed words. Yet one must remember that in the Penitential which is said to be of Theodore, certain things are handed down which are both repugnant to the doctrine of the Church and opposed to Theodore's own canons. Cf. c. X of the Council of Herudford under Theodore himself, celebrated A.D. 673, s. c.

For the rest, above we recited certain decrees both of Alexander II and of Paschal II, indeed also of Basil, in which mention is made of an impediment of the second or third genus of affinity then in force. Since it had been established in antiquity that, as far as kindred recognizes itself, nuptials were not lawful, and since affines in the second and third genus were accustomed to call themselves relatives, a custom was easily introduced that marriages should be interdicted among these also, although not according to the same degrees in each genus.

Innocent III removed the impediment from the second and third genus of affinity.

The prohibition also of conjugal copula shall henceforth not exceed the fourth degree of consanguinity and affinity, since in the further degrees a prohibition of this kind cannot now be generally observed without grave detriment.

Decree LI. We utterly inhibit clandestine marriages, also forbidding that any priest presume to be present at such; wherefore, extending generally to other places the special custom of certain places (cf. Constitutions of Odo, cited above), we establish that, when marriages are to be contracted, they be publicly proposed in the churches by the priests, a suitable term having been fixed beforehand so that within it whoever wishes and is able may oppose a legitimate impediment. And let the priests themselves nonetheless investigate whether any impediment stands in the way. But when a probable conjecture shall have appeared against the copula to be contracted, the contract is expressly interdicted, until, by manifest documents, it shall be established what ought to be done concerning it.

Not a simple doubt or conjecture, but a probable conjecture, that is, probable arguments, prohibit a marriage to be contracted before the Church gives sentence concerning it.

But if anyone shall have presumed to enter upon clandestine or interdicted marriages of this sort in a prohibited degree, even ignorantly, offspring received from such a conjunction shall be judged altogether illegitimate, to have no help from the ignorance of the parents ... In like manner the offspring shall be judged illegitimate if both parents, knowing a legitimate impediment, shall have presumed to contract in the sight of the Church, notwithstanding every interdiction.

Preface - Page VII