Article 8 — Whether the degrees of affinity extend in the same way as the degrees of consanguinity?

Objection 1: It would seem that the degrees of affinity do not extend in the same way as the degrees of consanguinity. For the tie of affinity is less strong than the tie of consanguinity, since affinity arises from consanguinity in diversity of species, as from an equivocal cause. Now the stronger the tie, the longer it lasts. Therefore, the tie of affinity does not last to the same number of degrees as consanguinity.

Obj. 2: Further, human law should imitate divine law. Now, according to the divine law certain degrees of consanguinity were forbidden, in which degrees affinity was not an impediment to marriage; for example, a man could marry a brother’s wife, though he could not marry her sister. Therefore, now too the prohibition of affinity and consanguinity should not extend to the same degrees.

On the contrary, A woman is connected with me by affinity from the very fact that she is married to a blood relation of mine. Therefore, in whatever degree her husband is related to me by blood, she is related to me in that same degree by affinity; and so the degrees of affinity should be reckoned in the same number as the degrees of consanguinity.

I answer that, Since the degrees of affinity are reckoned according to the degrees of consanguinity, the degrees of affinity must be the same in number as those of consanguinity. Nevertheless, affinity being a lesser tie than consanguinity, both formerly and now, a dispensation is more easily granted in the more remote degrees of affinity than in the remote degrees of consanguinity.

Reply Obj. 1: The fact that the tie of affinity is less than the tie of consanguinity causes a difference in the kind of relationship, but not in the degrees. Hence this argument is not to the point.

Reply Obj. 2: A man could not take his deceased brother’s wife except in order to raise up seed to his brother, in the case when the latter died without issue. This was requisite at a time when religious worship was propagated by means of the propagation of the flesh, which is not the case now. Hence it is clear that he did not marry her in his own person, as it were, but as supplying the place of his brother.