I answer that, In the union of Christ with the Church unity is found on either side. Consequently whether we find division of the flesh on the part of the husband, or on the part of the wife, there is a defect of sacrament. There is, however, a difference, because on the part of the husband it is required that he should not have married another wife, but not that he should be a virgin, whereas on the part of the wife it is also required that she be a virgin. The reason assigned by those versed in the Decretals is because the bridegroom signifies the Church militant which is entrusted to the care of a bishop, and in which there are many corruptions, while the spouse signifies Christ Who was a virgin: wherefore virginity on the part of the spouse, but not on the part of the bridegroom, is required in order that a man be made a bishop. This reason, however, is expressly contrary to the words of the Apostle (Eph. 5:25): "Husbands, love your wives, as Christ also loved the Church," which show that the bride signifies the Church, and the bridegroom Christ; and again he says (Eph. 5:23): "Because the husband is the head of the wife, as Christ is the head of the Church." Wherefore others say that Christ is signified by the bridegroom, and that the bride signifies the Church triumphant in which there is no stain. Also that the synagogue was first united to Christ as a concubine; so that the sacrament loses nothing of its signification if the bridegroom previously had a concubine. But this is most absurd, since just as the faith of ancients and of moderns is one, so is the Church one. Wherefore those who served God at the time of the synagogue belonged to the unity of the Church in which we serve God. Moreover this is expressly contrary to Jer. 3:14, Ezech. 16:8, Osee 2:16, where the espousals of the synagogue are mentioned explicitly: so that she was not as a concubine but as a wife. Again, according to this, fornication would be the sacred sign [sacramentum] of that union, which is absurd. Wherefore heathendom, before being espoused to Christ in the faith of the Church, was corrupted by the devil through idolatry. Hence we must say otherwise that irregularity is caused by a defect in the sacrament itself. Now when corruption of the flesh occurs outside wedlock on account of a preceding marriage, it causes no defect in the sacrament on the part of the person corrupted, but it causes a defect in the other person, because the act of one who contracts marriage terminates not in himself, but in the other party, wherefore it takes its species from its term, which, moreover, in regard to that act, is the matter as it were of the sacrament. Consequently if a woman were able to receive orders, just as her husband becomes irregular through marrying one who is not a virgin, but not through his not being a virgin when he marries, so also would a woman become irregular if she were to marry a man who is not a virgin, but not if she were no longer a virgin when she married ---unless she had been corrupted by reason of a previous marriage.
This suffices for the Reply to the First Objection.