Question I

GRATIAN. That it is lawful for us to take our own female blood relatives, or those of our wife, in marriage is proved by examples and authorities. For Abraham took Sarai, the daughter of his brother—namely, Lot’s sister—as wife. Isaac received Rebecca as spouse, who was the daughter of his mother’s male cousin. Jacob joined two sisters, namely Leah and Rachel, daughters of his maternal uncle Laban, to himself in marriage.

§ 1. In the law also, the Lord commanded Moses that no one should take a wife except from his own tribe and family. Likewise, if anyone died without children, the Lord commanded that his brother join the wife of the deceased to himself and raise up offspring from her for his brother. Moreover, all those to whom the law itself has come are proved to be bound by its precepts, except for those which are shown to have been nullified either by evangelical commands or apostolic institutions. But unions between blood relatives are found to be prohibited by no command of the Gospel or apostolic institution. Hence they are proved lawful now just as at the beginning.

§ 2. To these things the response is as follows: unions between blood relatives are found at one time to have been permitted on account of necessity, at another to have been commanded for a just reason. For when at the beginning one man and one woman from his side were formed by God, sisters were necessarily joined to brothers. But what is done under the compulsion of necessity ought likewise to cease when the necessity ceases. Therefore, union between blood relatives is now usurped all the more damnably insofar as it is proved less necessary. Hence a union of this kind is afterward found prohibited by the law, when the Lord says through Moses: “You shall not uncover the nakedness of your sister.” Hence Augustine says in the book The City of God, [XV, c. 16]:

Since, therefore, after the first union of the man made from dust and of his spouse from the man’s side, the human race had need of the commingling of males and females in order that they might be multiplied by begetting, and there were no human beings except those born from those two, the men took their sisters as spouses. Certainly, the more ancient this is because necessity compelled it, the more damnable it afterward became when religion prohibited it. For the most certain consideration of charity was had: that human beings, for whom useful and most honorable concord was fitting, should be bound together by the bonds of diverse relationships; that one person should not have many relationships in one person, but individual relationships should be spread among individual persons, and thus many relationships might more diligently bind many persons to social life. For “father” and “father-in-law” are names of two relationships. Therefore, when someone has one man as father and another as father-in-law, charity extends itself more numerously. But the one Adam was compelled to be both to his sons and to his daughters when brothers and sisters were joined in marriage. Thus Eve his wife also was both mother-in-law and mother to the children of each sex. If these had been two women, one the mother and the other the mother-in-law, social affection would have bound itself more abundantly.

§ 1. But at that time there was no source from which this could be done, when there were no human beings from those first two except brothers and sisters. Therefore, what could be done had to be done, so that, when there existed an abundance of women from whom wives could be taken who were now not sisters, that former thing would not only not be done where there was no necessity.

§ 2. With the human race increasing, we discern that this is so observed even among impious worshipers of many false gods that, even if marriages between brother and sister are permitted by perverse laws, a better custom nevertheless prefers to shudder at that very license and so opposes it as though it could never have been lawful.

§ 3. Therefore, the joining of male and female, insofar as it concerns the human race, is a certain seedbed of charity; but the heavenly city has need, so that it may escape the harm of generation.

GRATIAN. Accordingly, Abraham, Isaac, Jacob, and the others who took wives from their own kindred are excused by this custom, which took its origin from the very beginning of human propagation and which no law had nullified by commanding the contrary. Yet another cause of most right reason, on account of which this was done, can also be understood. While all the others were defiled by idolatry, only the family of Eber remained in the worship of the one God. Hence Abraham was cast by the Chaldeans with his brother into the fire which he refused to worship, so that by burning he might experience the divine power of its divinity, which he had disdained to worship with veneration. Therefore, lest believers slide into idolatry through union with unbelievers and so offend God—as once before the flood the sons of God, mingled with the daughters of men, had provoked him to anger—it was most rightly provided that the patriarchs, most holy men, should take wives for themselves only from their own kindred, that is, from the family of believers. Hence also, when the children of Israel, as they were about to enter the promised land, heard from the Lord that they were not to take the daughters of the Canaanites as wives for themselves nor give their own daughters to them in marriage, the Lord immediately added: “Lest they cause you to withdraw from your God and fornicate with strange gods.” Hence also Ezra ordered that the Idumaean women and women of other nations, through whom the children of Israel were going to strange gods, be separated from them.

§ 1. There is also another cause why unions between blood relatives in the people of God were first permitted, or rather commanded. From the beginning God so ordered the salvation of the human race that he established the primitive Church among that people who were near to him by consanguinity of the flesh. Hence he first chose the Apostles from the Jewish people and established them as the foundation of the Church; by their preaching many from the same people, having been converted to God, furnished in themselves the origin of the Church. Thereafter, the Jewish people having been abandoned in the blindness of their unbelief, the preaching of the Gospel was transferred to the nations, who were alien from Christ both in faith and in kinship of the flesh; and Christ, as though spurning union with a female blood relative, chose for himself a wife from an alien kindred, fulfilling what he had foretold through the prophet: “In your sins I sent away your mother as an adulteress and a repudiated woman.” And likewise through another Prophet: “I shall call the people not mine my people.” Therefore, as a sacrament of this matter, unions between blood relatives were at first permitted among the people but are now prohibited. And because a faithful people is found not only in one family but in the whole multitude of nations, each person is permitted to take a wife not from his own kindred but from any other.

§ 2. But that statement that the precepts of the law which are proved to have been nullified neither by evangelical nor apostolic institutions are to be observed is indeed true; but since the Apostle proves that all figurative things were given for a time, and therefore affirms that, when the truth comes, those things are no longer to be observed, and since this, as was shown above, is proved to have been instituted by God for the sake of a sacrament, it is most certainly established that this too was revoked together with the other figurative things. Nevertheless, just as the Apostle by way of counsel added certain things which were not found defined by evangelical precepts, and yet were not therefore repudiated by the other Apostles as rash or superfluous, so also the Church, after the apostolic institutions, added certain things by a counsel of perfection, such as those concerning the continence of ministers, the confection of the mysteries, and the celebration of the offices; these are in no way to be repudiated but are to be received with diligent veneration. Therefore, although unions between blood relatives are not found prohibited by evangelical and apostolic precepts, they are nevertheless to be avoided, because they are found to have been delimited by ecclesiastical institutions.