In Roman law, divorce was equally available to both the husband and the wife, even without the other party’s consent, at least until 331 CTh 3,16,1, when the possibility of unilateral divorce was limited to particular cases. The wife could be repudiated only for adultery, witchcraft or acting as a procuress; the husband for murder, witchcraft or grave-robbing. Those convicted of these crimes were already subject to capital punishment; therefore, if a unilateral divorce was not initiated for one of these reasons, the initiating party incurred a penalty on the dowry, and the woman was sent away. This law was revoked under Julian, but revived from the mid-5th c. This notwithstanding, unilateral divorce remained valid, whereas divorce with the consent of both parties continued to be freely available. This was the context in which the bishops and theologians began their great fight against the practice of divorce.
If, theoretically, they did not recognize unilateral divorce nor consensual divorce either, based on the NT there were two cases in which separation was permitted: adultery Mt 5:32; 19:9, and the difference of religion 1 Cor 7:12-16 of one party, this latter in the case where a person, married when both spouses were pagan, converts, and the other spouse is unable to live in peace with him or her. The validity of each reason had different force: with a partner’s adultery, for most Fathers beginning from Hermas, separation was obligatory; for others, it was merely a concession. According to Hermas, Basil of Ancyra, Theodoret and Augustine, the guilty party who accepts correction must be taken back; this could not be done according to John Chrysostom, Basil of Caesarea, Cyril of Alexandria and Jerome, based on Dt 24:1-4. In the case of the conversion of one of the two pagan parties, Augustine requires that the initiative in separating not come from the believer, and he exhorts the Christian spouse to do everything possible to avoid it. Despite the polemic of Clement of Alexandria and Origen against heretics who dissolved marriages for religious reasons, Basil of Caesarea Mor. 73,1; Great Asketicon 12 admitted separation in order to enter religious life.
When considering divorce, however, one must distinguish between the separation of the spouses and the possibility of contracting a new marriage: this latter problem, posed to moderns by Mt 19:9, didn’t trouble the ancients at all, except for a few 4th-5th-c. Latin authors, because they read that text in the form of Mt 5:32 which may have been the original form, where a new marriage of the initiator is not spoken of. The situation is different in the case of the other reason for separation: the passage clearly says that the converted partner may remarry. Paradoxically, a second marriage contracted after a separation that has occurred because of an unbelieving spouse is admitted only by Ambrosiaster with the same conditions for both sexes. Conversely, along with other Fathers, Augustine formally opposed it Con. adult. 1,13-24: according to him, the unbeliever was also bound not to remarry, based on Gen 2:24: thus in antiquity the Pauline privilege meant nothing more than the possibility of separation, but without permission for a new marriage.