Whether the degrees of consanguinity that are an impediment to marriage could be fixed by the Church?

❌ Objection 1 : It would seem that the degrees of consanguinity that are an impediment to marriage could not be fixed by the Church so as to reach to the fourth degree. For it is written (Mt. 19:6): "What God hath joined together let no man put asunder." But God joined those together who are married within the fourth degree of consanguinity, since their union is not forbidden by the Divine law. Therefore they should not be put asunder by a human law.

❌ Objection 2 : Further, matrimony is a sacrament as also is baptism. Now no ordinance of the Church could prevent one who is baptized from receiving the baptismal character, if he be capable of receiving it according to the Divine law. Therefore neither can an ordinance of the Church forbid marriage between those who are not forbidden to marry by the Divine law.

❌ Objection 3 : Further, positive law can neither void nor extend those things which are natural. Now consanguinity is a natural tie which is in itself of a nature to impede marriage. Therefore the Church cannot by its ordinance permit or forbid certain people to marry, any more than she can make them to be kin or not kin.

❌ Objection 4 : Further, an ordinance of positive law should have some reasonable cause, since it is for this reasonable cause that it proceeds from the natural law. But the causes that are assigned for the number of degrees seem altogether unreasonable, since they bear no relation to their effect; for instance, that consanguinity be an impediment as far as the fourth degree on account of the four elements as far as the sixth degree on account of the six ages of the world, as far as the seventh degree on account of the seven days of which all time is comprised. Therefore seemingly this prohibition is of no force.

❌ Objection 5 : Further, where the cause is the same there should be the same effect. Now the causes for which consanguinity is an impediment to marriage are the good of the offspring, the curbing of concupiscence, and the extension of friendship, as stated above (Article [3]), which are equally necessary for all time. Therefore the degrees of consanguinity should have equally impeded marriage at all times: yet this is not true since consanguinity is now an impediment to marriage as far as the fourth degree, whereas formerly it was an impediment as far as the seventh.

❌ Objection 6 : Further, one and the same union cannot be a kind of sacrament and a kind of incest. But this would be the case if the Church had the power of fixing a different number in the degrees which are an impediment to marriage. Thus if certain parties related in the fifth degree were married when that degree was an impediment, their union would be incestuous, and yet this same union would be a marriage afterwards when the Church withdrew her prohibition. And the reverse might happen if certain degrees which were not an impediment were subsequently to be forbidden by the Church. Therefore seemingly the power of the Church does not extend to this.

❌ Objection 7 : Further, human law should copy the Divine law. Now according to the Divine law which is contained in the Old Law, the prohibition of degrees does not apply equally in the ascending and descending lines: since in the Old Law a man was forbidden to marry his father's sister but not his brother's daughter. Therefore neither should there remain now a prohibition in respect of nephews and uncles.