IV. In the case of trigamy and polygamy they laid down the same rule, in proportion, as in the case of digamy; namely one year for digamy (some authorities say two years); for trigamy men are separated for three and often for four years; but this is no longer described as marriage at all, but as polygamy; nay rather as limited fornication. It is for this reason that the Lord said to the woman of Samaria, who had five husbands, “he whom thou now hast is not your husband.” He does not reckon those who had exceeded the limits of a second marriage as worthy of the title of husband or wife. In cases of trigamy we have accepted a seclusion of five years, not by the canons, but following the precept of our predecessors. Such offenders ought not to be altogether prohibited from the privileges of the Church; they should be considered deserving of hearing after two or three years, and afterwards of being permitted to stand in their place; but they must be kept from the communion of the good gift, and only restored to the place of communion after showing some fruit of repentance.
V. Heretics repenting at death ought to be received; yet to be received, of course, not indiscriminately, but on trial of exhibition of true repentance and of producing fruit in evidence of their zeal for salvation.
VI. The fornication of canonical persons is not to be reckoned as wedlock, and their union is to be completely dissolved, for this is both profitable for the security of the Church and will prevent the heretics from having a ground of attack against us, as though we induced men to join us by the attraction of liberty to sin.
VII. Abusers of themselves with mankind, and with beasts, as also murderers, wizards, adulterers, and idolaters, are deserving of the same punishment. Whatever rule you have in the case of the rest, observe also in their case. There can, however, be no doubt that we ought to receive those who have repented of impurity committed in ignorance for thirty years. In this case there is ground for forgiveness in ignorance, in the spontaneity of confession, and the long extent of time. Perhaps they have been delivered to Satan for a whole age of man that they may learn not to behave unseemly; wherefore order them to be received without delay, specially if they shed tears to move your mercy, and show a manner of living worthy of compassion.
VIII. The man who in a rage has taken up a hatchet against his own wife is a murderer. But it is what I should have expected from your intelligence that you should very properly remind me to speak on these points more fully, because a wide distinction must be drawn between cases where there is and where there is not intent. A case of an act purely unintentional, and widely removed from the purpose of the agent, is that of a man who throws a stone at a dog or a tree, and hits a man. The object was to drive off the beast or to shake down the fruit. The chance comer falls fortuitously in the way of the blow, and the act is unintentional. Unintentional too is the act of any one who strikes another with a strap or a flexible stick, for the purpose of chastising him, and the man who is being beaten dies. In this case it must be taken into consideration that the object was not to kill, but to improve, the offender. Further, among unintentional acts must be reckoned the case of a man in a fight who when warding off an enemy's attack with cudgel or hand, hits him without mercy in some vital part, so as to injure him, though not quite to kill him. This, however, comes very near to the intentional; for the man who employs such a weapon in self defence, or who strikes without mercy, evidently does not spare his opponent, because he is mastered by passion. In like manner the case of any one who uses a heavy cudgel, or a stone too big for a man to stand, is reckoned among the unintentional, because he does not do what he meant: in his rage he deals such a blow as to kill his victim, yet all he had in his mind was to give him a thrashing, not to do him to death. If, however, a man uses a sword, or anything of the kind, he has no excuse: certainly none if he throws his hatchet. For he does not strike with the hand, so that the force of the blow may be within his own control, but throws, so that from the weight and edge of the iron, and the force of the throw, the wound cannot fail to be fatal.
On the other hand acts done in the attacks of war or robbery are distinctly intentional, and admit of no doubt. Robbers kill for greed, and to avoid conviction. Soldiers who inflict death in war do so with the obvious purpose not of fighting, nor chastising, but of killing their opponents. And if any one has concocted some magic philtre for some other reason, and then causes death, I count this as intentional. Women frequently endeavour to draw men to love them by incantations and magic knots, and give them drugs which dull their intelligence. Such women, when they cause death, though the result of their action may not be what they intended, are nevertheless, on account of their proceedings being magical and prohibited, to be reckoned among intentional homicides. Women also who administer drugs to cause abortion, as well as those who take poisons to destroy unborn children, are murderesses. So much on this subject.
IX. The sentence of the Lord that it is unlawful to withdraw from wedlock, save on account of fornication, applies, according to the argument, to men and women alike. Custom, however, does not so obtain. Yet, in relation with women, very strict expressions are to be found; as, for instance, the words of the apostle “He which is joined to a harlot is one body” and of Jeremiah, If a wife “become another man's shall he return unto her again? Shall not that land be greatly polluted?” And again, “He that has an adulteress is a fool and impious.” Yet custom ordains that men who commit adultery and are in fornication be retained by their wives. Consequently I do not know if the woman who lives with the man who has been dismissed can properly be called an adulteress; the charge in this case attaches to the woman who has put away her husband, and depends upon the cause for which she withdrew from wedlock. In the case of her being beaten, and refusing to submit, it would be better for her to endure than to be separated from her husband; in the case of her objecting to pecuniary loss, even here she would not have sufficient ground. If her reason is his living in fornication we do not find this in the custom of the church; but from an unbelieving husband a wife is commanded not to depart, but to remain, on account of the uncertainty of the issue. “For what do you know, O wife, whether you shall save your husband?” Here then the wife, if she leaves her husband and goes to another, is an adulteress. But the man who has been abandoned is pardonable, and the woman who lives with such a man is not condemned. But if the man who has deserted his wife goes to another, he is himself an adulterer because he makes her commit adultery; and the woman who lives with him is an adulteress, because she has caused another woman's husband to come over to her.
Source: Letters (New Advent)