Objection 1: It would seem that marriage is not annulled by the husband committing incest with his wife's sister. For the wife should not be punished for her husband's sin. Yet she would be punished if the marriage were annulled. Therefore, etc.
Objection 2: Further, it is a greater sin to know one's own relative, than to know the relative of one's wife. But the former sin is not an impediment to marriage. Therefore neither is the second.
Objection 3: Further, if this is inflicted as a punishment of the sin, it would seem, if the incestuous husband marry even after his wife's death, that they ought to be separated: which is not true.
Objection 4: Further, this impediment is not mentioned among those enumerated above (Q[50]). Therefore it does not void the marriage contract.
On the contrary, By knowing his wife's sister he contracts affinity, with his wife. But affinity voids the marriage contract. Therefore the aforesaid incest does also.
Further, by whatsoever a man sinneth, by the same also is he punished. Now such a man sins against marriage. Therefore he ought to be punished by being deprived of marriage.
I answer that, If a man has connection with the sister or other relative of his wife before contracting marriage, even after his betrothal, the marriage should be broken off on account of the resultant affinity. If, however, the connection take place after the marriage has been contracted and consummated, the marriage must not be altogether dissolved: but the husband loses his right to marital intercourse, nor can he demand it without sin. And yet he must grant it if asked, because the wife should not be punished for her husband's sin. But after the death of his wife he ought to remain without any hope of marriage, unless he receive a dispensation on account of his frailty, through fear of unlawful intercourse. If, however, he marry without a dispensation, he sins by contravening the law of the Church, but his marriage is not for this reason to be annulled. This suffices for the Replies to the Objections, for incest is accounted an impediment to marriage not so much for its being a sin as on account of the affinity which it causes. For this reason it is not mentioned with the other impediments, but is included in the impediment of affinity.
Whether defective age is an impediment to marriage?
Objection 1: It would seem that deficient age is not an impediment to marriage. For according to the laws children are under the care of a guardian until their twenty-fifth year. Therefore it would seem that before that age their reason is not sufficiently mature to give consent, and consequently that ought seemingly to be the age fixed for marrying. Yet marriage can be contracted before that age. Therefore lack of the appointed age is not an impediment to marriage.
Objection 2: Further, just as the tie of religion is perpetual so is the marriage tie. Now according to the new legislation (cap. Non Solum, De regular. et transeunt.) no one can be professed before the fourteenth year of age. Therefore neither could a person marry if defective age were an impediment.
Objection 3: Further, just as consent is necessary for marriage on the part of the man, so is it on the part of the woman. Now a woman can marry before the age of fourteen. Therefore a man can also.
Objection 4: Further, inability to copulate, unless it be perpetual and not known, is not an impediment to marriage. But lack of age is neither perpetual nor unknown. Therefore it is not an impediment to marriage.
Objection 5: Further, it is not included under any of the aforesaid impediments (Q[50]), and consequently would seem not to be an impediment to marriage.
On the contrary, A Decretal (cap. Quod Sedem, De frigid et malefic.) says that "a boy who is incapable of marriage intercourse is unfit to marry." But in the majority of cases he cannot pay the marriage debt before the age of fourteen (De Animal. vii). Therefore, etc.
Further, "There is a fixed limit of size and growth for all things in nature" according to the Philosopher (De Anima ii, 4): and consequently it would seem that, since marriage is natural, it must have a fixed age by defect of which it is impeded.
I answer that, Since marriage is effected by way of a contract, it comes under the ordinance of positive law like other contracts. Consequently according to law (cap. Tua, De sponsal. impub.) it is determined that marriage may not be contracted before the age of discretion when each party is capable of sufficient deliberation about marriage, and of mutual fulfilment of the marriage debt, and that marriages otherwise contracted are void. Now for the most part this age is the fourteenth year in males and the twelfth year in women: but since the ordinances of positive law are consequent upon what happens in the majority of cases, if anyone reach the required perfection before the aforesaid age, so that nature and reason are sufficiently developed to supply the lack of age, the marriage is not annulled. Wherefore if the parties who marry before the age of puberty have marital intercourse before the aforesaid age, their marriage is none the less perpetually indissoluble.
Reply to Objection 1: In matters to which nature inclines there is not required such a development of reason in order to deliberate, as in other matters: and therefore it is possible after deliberation to consent to marriage before one is able to manage one's own affairs in other matters without a guardian.
Reply to Objection 2: The same answer applies, since the religious vow is about matters outside the inclination of nature, and which offer greater difficulty than marriage.
Reply to Objection 3: It is said that woman comes to the age of puberty sooner than man does (De Animal. ix); hence there is no parallel between the two.
Reply to Objection 4: In this case there is an impediment not only as to inability to copulate, but also on account of the defect of the reason, which is not yet qualified to give rightly that consent which is to endure in perpetuity.
Reply to Objection 5: The impediment arising from defective age, like that which arises from madness, is reducible to the impediment of error; because a man has not yet the full use of his free-will.