Objection 1: It would seem that the Church ought not to excommunicate anyone, because excommunication is a kind of curse, and we are forbidden to curse (Rom 12:14). Therefore, the Church should not excommunicate.

Obj. 2: Further, the Church Militant should imitate the Church Triumphant. Now we read in the epistle of Jude 1:9 that when Michael the Archangel disputing with the devil contended about the body of Moses, he did not dare to bring against him the judgment of blasphemy, but said, “May the Lord rebuke you.” Therefore, the Church Militant ought not to judge any man by cursing or excommunicating him.

Obj. 3: Further, no man should be given into the hands of his enemies, unless there be no hope for him. Now by excommunication a man is given into the hands of Satan, as is clear from 1 Corinthians 5:5. Since, then, we should never give up hope about anyone in this life, the Church should not excommunicate anyone.

On the contrary, The Apostle ordered a man to be excommunicated (1 Cor 5:5).

Further, It is written about the man who refuses to hear the Church: let him be to you as the heathen or publican (Matt 18:17). But heathens are outside the Church. Therefore, they also who refuse to hear the Church should be banished from the Church by excommunication.

I answer that, The judgment of the Church should be conformed to the judgment of God. Now God punishes the sinner in many ways in order to draw him to good, either by chastising him with stripes, or by leaving him to himself so that, being deprived of those helps whereby he was kept out of evil, he may acknowledge his weakness, and humbly return to God whom he had abandoned in his pride. In both these respects the Church by passing sentence of excommunication imitates the judgment of God. For by severing a man from the communion of the faithful that he may blush, she imitates the judgment whereby God chastises man with stripes; and by depriving him of prayers and other spiritual things, she imitates the judgment of God in leaving man to himself, in order that by humility he may learn to know himself and return to God.

Reply Obj. 1: A curse may be pronounced in two ways: first, so that the intention of the one who curses is fixed on the evil which he invokes or pronounces, and cursing in this sense is altogether forbidden. Second, so that the evil which a man invokes in cursing is intended for the good of the one who is cursed, and thus cursing is sometimes lawful and salutary: thus a physician makes a sick man undergo pain, for instance, by cutting him in order to deliver him from his sickness.

Reply Obj. 2: The devil cannot be brought to repentance, wherefore the pain of excommunication cannot do him any good.

Reply Obj. 3: From the very fact that a man is deprived of the prayers of the Church, he incurs a triple loss, corresponding to the three things which a man acquires through the Church’s prayers. For they bring an increase of grace to those who have it, or merit grace for those who have it not; and in this respect the Master of the Sentences says: the grace of God is taken away by excommunication (Sentences IV, D. 18).

They also prove a safeguard of virtue; and in this respect he says that protection is taken away, not that the excommunicated person is withdrawn altogether from God’s providence, but that he is excluded from that protection with which he watches over the children of the Church in a more special way. Moreover, they are useful as a defense against the enemy, and in this respect he says that the devil receives greater power of assaulting the excommunicated person, both spiritually and corporally.

Hence in the early Church, when men had to be enticed to the faith by outward signs (thus the gift of the Holy Spirit was shown openly by a visible sign), so too excommunication was evidenced by a person being troubled in his body by the devil. Nor is it unreasonable that one for whom there is still hope be given over to the enemy, for he is given not to damnation, but to correction, since the Church has the power to rescue him from the hands of the enemy, whenever he is willing.