OF THE IMPEDIMENT OF AFFINITY (ELEVEN ARTICLES)
We must consider next the impediment of affinity. Under this head there are eleven points of inquiry:
(1) Whether affinity results from matrimony?
(2) Whether it remains after the death of husband or wife?
(3) Whether it is caused through unlawful intercourse?
(4) Whether it arises from a betrothal?
(5) Whether affinity is caused through affinity?
(6) Whether affinity is an impediment to marriage?
(7) Whether affinity in itself admits of degrees?
(8) Whether its degrees extend as far as the degrees of consanguinity?
(9) Whether marriages of persons related to one another by consanguinity or affinity should always be dissolved by divorce?
(10) Whether the process for the dissolution of like marriages should always be by way of accusation?
(11) Whether witnesses should be called in such a case?
Whether a person contracts affinity through the marriage of a blood-relation?
Objection 1: It would seem that a person does not contract affinity through the marriage of a blood-relation. For "the cause of a thing being so is yet more so." Now the wife is not connected with her husband's kindred except by reason of the husband. Since then she does not contract affinity with her husband, neither does she contract it with her husband's kindred.
Objection 2: Further, if certain things be separate from one another and something be connected with one of them, it does not follow that it is connected with the other. Now a person's blood relations are separate from one another. Therefore it does not follow, if a certain woman be married to a certain man, that she is therefore connected with all his kindred.
Objection 3: Further, relations result from certain things being united together. Now the kindred of the husband do not become united together by the fact of his taking a wife. Therefore they do not acquire any relationship of affinity.
On the contrary, Husband and wife are made one flesh. Therefore if the husband is related in the flesh to all his kindred, for the same reason his wife will be related to them all.
Further, this is proved by the authorities quoted in the text (Sent. iv, D, 41).
I answer that, A certain natural friendship is founded on natural fellowship. Now natural fellowship, according to the Philosopher (Ethic. viii, 12), arises in two ways; first, from carnal procreation; secondly, from connection with orderly carnal procreation, wherefore he says (Ethic. viii, 12) that the friendship of a husband towards his wife is natural. Consequently even as a person through being connected with another by carnal procreation is bound to him by a tie of natural friendship, so does one person become connected with another through carnal intercourse. But there is a difference in this, that one who is connected with another through carnal procreation, as a son with his father, shares in the same common stock and blood, so that a son is connected with his father's kindred by the same kind of tie as the father was, the tie, namely of consanguinity, albeit in a different degree on account of his being more distant from the stock: whereas one who is connected with another through carnal intercourse does not share in the same stock, but is as it were an extraneous addition thereto: whence arises another kind of tie known by the name of "affinity." This is expressed in the verse:
Marriage makes a new kind of connection,
While birth makes a new degree,
because, to wit, the person begotten is in the same kind of relationship, but in a different degree, whereas through carnal intercourse he enters into a new kind of relationship.
Reply to Objection 1: Although a cause is more potent than its effect, it does not always follow that the same name is applicable to the cause as to the effect, because sometimes that which is in the effect, is found in the cause not in the same but in a higher way; wherefore it is not applicable to both cause and effect under the same name or under the same aspect, as is the case with all equivocal effective causes. Thus, then, the union of husband and wife is stronger than the union of the wife with her husband's kindred, and yet it ought not to be named affinity, but matrimony which is a kind of unity; even as a man is identical with himself, but not with his kinsman.
Reply to Objection 2: Blood-relations are in a way separate, and in a way connected: and it happens in respect of their connection that a person who is connected with one of them is in some way connected with all of them. But on account of their separation and distance from one another it happens that a person who is connected with one of them in one way is connected with another in another way, either as to the kind of connection or as to the degree.