Liber II, Pars I — Quod decet omnes cives, et maxime omnes reges et principes non ducere coniuges sibi nimia consanguineitate coniunctas. Cap. XI.

Liber II, Pars I — Quod decet omnes cives, et maxime omnes reges et principes non ducere coniuges sibi nimia consanguineitate coniunctas. Cap. XI.

Someone might believe (while a woman is married to one man) that it is permissible for that marriage to occur, regardless of the kind or degree of kinship between the husband and wife. But this is contrary to the dictates of reason: that one should not enter into marriage with parents or close relatives. The first reason comes from the respect that is due to parents and relatives. The second reason arises from the good that comes from marriage. The third reason is based on the evil that is avoided through this prohibition. The first reason is clear. For since we owe our parents a proper subjection and our relatives a proper respect, when this respect is not maintained between husband and wife due to mutual obligations, natural reason dictates that those who are too closely related by blood should not be joined in marriage. Indeed, it seems to align with natural reason that there are hardly any peoples who do not exclude certain individuals from entering into marriage. Therefore, the Philosopher says. It is fitting. Natural reason excludes certain persons from entering into marriage: for it has never been permitted to anyone, nor have we found it allowed among any peoples, to contract marriage with one's mother. For since a wife ought to be subject to her husband, it would be inappropriate for a mother to be subject to her son. Therefore, it is not permissible for children to marry their parents because of the mutual respect they owe each other. Also, it is not allowed for them to marry other relatives if they are closely related by blood, except in cases of dispensation. For, on account of some great good that could arise from it, it is sometimes granted to someone in a particular case what is generally denied to others. Therefore, due to the reverence owed to relatives, which cannot be properly maintained in actions between spouses (except by dispensation and in special cases), marriages should not be contracted between persons who are closely related by blood. It is fitting, therefore, that all citizens should not enter into marriage with any persons. This is especially true for kings and princes, as they should observe the natural order even more closely. The second way to investigate this same issue is drawn from a certain good that arises from marriage. For it was said in the preceding chapter that peace and harmony arise from the bond of marriage between those who enter into it. However, when there is sufficient friendship among relatives due to their close kinship, natural reason dictates that marriages should be contracted between those who are not too closely related. Thus, it is fitting that all citizens should not marry those who are too closely related; this is even more important for kings and princes, because the higher their status and rank, the more they need the support and friendship of others. For according to the Philosopher in Ethics, the taller a tree is, the more it needs support, so it doesn't get shaken by the wind. Therefore, kings and princes, the higher their rank, the more they need to have greater and more numerous relatives, both by blood and by friendship. The third way to investigate this same matter is derived from the evil that is avoided through marriage. For through marriage, not only is the good of offspring produced, but the evil of intemperance is also avoided; for those who cannot maintain chastity, lest they become too intemperate by mixing with any women, it is beneficial for them to enter into marriage, so that being content with one wife, they may be restrained from intemperance. For when the desires of the flesh, if excessive, strike at reason, as we have often said above, it is beneficial for anyone wishing to live according to reason and intellect not to give excessive attention to carnal matters. Thus, when there is a natural love for persons connected by excessive kinship, if marital friendship is added to that love, the affection between spouses will increase so much that they should be able to avoid excessive indulgence in carnal matters. Therefore, all citizens should not enter into marriage with persons who are too closely related; lest by giving too much attention to carnal matters, their reason be struck down, and they be diverted from their proper duties and civil works. This is especially true for kings and princes, who ought to be more vigilant in wisdom and understanding; and the greater the danger that can arise for a kingdom, if kings and princes do not diligently attend to the welfare of the kingdom and to civil affairs. In cases of excessive proximity in kinship, marriage should not be contracted. However, in the third and fourth degrees, which begin to deviate from close kinship, if there is a dispensation for some good to be pursued, or to avoid a great evil, a marital bond may be contracted.