Summa contra Gentiles3.123 Chapter CXXIII. That matrimony should be indissoluble

If one consider the matter rightly, it will be seen that the foregoing arguments not only show that the fellowship of male and female in human nature, which we call matrimony, should be lasting, but also that it should endure throughout life.

For possessions are directed to the preservation of the natural life: and since the natural life which cannot be preserved in the person of an undying father, is preserved, by a kind of succession, in the person of the son, it is naturally befitting that the son succeed in things belonging to the father. Therefore it is natural that the father’s care for his son should endure to the end of his life. If, then, the father’s care for his son causes, even among birds, the continued fellowship of male and female, the natural order demands that in the human species father and mother should remain together to the end of life.

It would seem also contrary to equity for the aforesaid fellowship to be dissolved. For the female requires the male, not only for procreation, as in other animals, but also for governance: because the male excels both in intelligence and in strength. Now, the woman is taken into partnership with the man for the purpose of procreation. Consequently when the woman ceases to be fruitful and fair, this is an obstacle against her being taken by another man. Hence, if a man after taking a wife in her youth, while she is yet fair and fruitful, can put her away when she has aged, he does her an injury, contrary to natural equity.

Again. It is clearly unfitting that the woman be allowed to put away the man: since she is naturally subject to the man’s authority: and one who is subject to another is not free to withdraw himself from his authority. Hence it would be contrary to the natural order if a wife could leave her husband. Consequently, if the husband could leave his wife, there would not be just fellowship between husband and wife, but a kind of slavery on the part of the latter.

Also. There is in man a certain natural anxiety to be assured of his offspring: and this is necessary, because the child needs the father’s authority for a long time. Hence whatever prevents him from being assured of having children, is contrary to the natural instinct of the human species. Now, if the husband may put away his wife, or the wife leave her husband, and take another man, thus being copulated first to one, and afterwards to another, the certainty of offspring would be hindered. Therefore it is contrary to the natural instinct of the human species that husband and wife be separated: and in consequence the union of male and female in the human race must be not only long lasting but indissoluble.

Moreover. The greater the friendship the more stable and lasting is it. Now, seemingly. between husband and wife there is the greatest friendship: for they are made one not only in the act of carnal intercourse, which even among dumb animals causes an agreeable fellowship, but also as partners in the whole intercourse of daily life: so that, to indicate this, man must leave father and mother (Gen. ii. 24) for his wife’s sake. Therefore it is right that matrimony should be altogether indissoluble. It must also be observed that among natural acts generation alone is directed to the common good: since eating, and the discharge of other superfluities, regard the individual: whereas procreation regards the preservation of the species. Hence, as the law is made for the common good, whatever regards procreation should be regulated, before other things, by laws both divine and human. Now positive laws should be based on natural instinct, if they be human: even as in demonstrative sciences, all human discoveries must needs be founded on principles naturally known. And if they be divine, not only do they express the instinct of nature, but they also supply the defect of natural instinct: even as the things that God reveals, are beyond the grasp of natural reason. Since, then, the natural instinct of the human species is that the union of male and female be indissoluble, and that one man be united to one woman, it behoved this to be ordered by human law. Moreover, the divine law adds a kind of supernatural reason taken from the representation of the indissoluble union of Christ and the Church, which is union of one with one. Wherefore inordinateness in the act of generation not only is contrary to the natural instinct, but it also transgresses laws both divine and human. Hence, this kind of disorder is more sinful than that which may occur in taking food, or in similar things.

And since in man all other things should be subordinate to what is best in him, the union of male and female is ordered by law not only in the point of its relation to the procreation of children, as in other animals, but also in its relation to good morals, which right reason regulates, both as regards man in himself, and considered as a member either of a private family, or of the civil community. Now, the indissolubility of the union of male and female belongs to good morals. Because their mutual love will be the more constant if they know that they are indissolubly united. They will also be more carefully provident in the conduct of the household, when they realize that they are always to remain together in possession of the same things. Again, this precludes the origin of quarrels which must needs arise between the husband and his wife’s relatives, if he were to put his wife away: and those who are connected through affinity have a greater regard for one another. Moreover it removes the occasions of adultery which would occur, were the husband free to put away his wife, or vice versa: for this would encourage the seeking of further marriage.

Hence it is said (Matth. v. 31; xix. 9; 1 Cor. vii. 10): But I say to you that the wife depart not from her husband.

Hereby we condemn the custom of putting a wife away. Nevertheless this was permitted to the Jews in the Old Law by reason of the hardness of their heart: because, to wit, they were prone to wife-murder. Hence the lesser evil was allowed, in order to avoid the greater.