His defence is an appeal to the principle of double effect. In other words, because the intention of the HIV positive partner is not to transmit the virus to his or her spouse, the use of the prophylactic is not intended to exclude God's place as Creator in the act of union, but to strive to reduce significantly the chance of infection of his spouse.
The fact that every single time (assuming that the condom does not fail) he makes love to his wife, the outcome may be to exclude God's creative purpose in lovemaking is, he holds, an unintended side effect, thereby not just mitigating, but removing the guilt that would have been his.
The example cited by Church theologians is that of a doctor who gives more morphine to a patient than usual with the intention of relieving pain. Even if that dose of morphine kills the patient, it is asserted, the doctors intention was to reduce pain, therefore he is not guilty of wrongdoing. The question is, does this work with condoms in marriage where one person is HIV positive?
My opinion, and yes I know it is just my opinion (though I am far from alone in holding it), is that such an action is totally out of keeping with the Faith in the Holy Tradition of the Church. Condoms may hold water, but they have never held theological water in the Church's Tradition. Never. For spouses, one of whom is infected with the disease, which moral duty is more important? The duty to 'make love'? Or the duty to make love while giving each other totally to one another? Or the duty to make love, giving each other totally to one another and be open to new life?
I would argue strongly that traditional Catholic Teaching does not look upon the sexual act in marriage merely as 'love-making' in the secular view, for 'making love' in the secular view would not readily reject condoms dogmatically as contrary to the purpose of the act. The Church, certainly since Pope John Paul II, sees the sexual act in marriage as both unitive and procreative. The use of the condom is not sinful just because its 'side effect' is to deny Almighty God His sovereign, creative purpose in the creation of new life. The use of the condom is sinful also on the grounds that it denies the unitive aspect of the sexual act. The use of the condom is doubly gravely sinful because it denies both the procreative and the unitive aspects of the marital act. It denies not one, but both of the purposes of sex within marriage. Its application within marriage, even with good intentions, denies and destroys the whole purpose of sex.
Why do condoms attack the unitive purpose of the sexual act in marriage? Because Our Blessed Lord said that when a man and a woman leave their mother and father they marry and become 'one flesh'. The whole Holy Tradition of the Holy Church reflects that a man and woman become 'one flesh' in marriage, and, give themselves to each other totally, without reservation. The condom is a barrier not just between a couple and God's creative right in marriage. It is a barrier between the man and the woman themselves in the sexual act. For these two reasons, even if the intention is good, the whole Tradition of the Church rejects the condom's application in marriage.
If, therefore, a man and a woman are suddenly unable to express their love for each other totally in the Sacrament of Marriage, then the only truly Catholic response is to say that both have met the painful Cross of Our Lord Jesus Christ. It is through the Cross of Our Lord Jesus Christ that this couple therefore enter into a new understanding of love which is definitively chaste. It is an opportunity for a couple to enter into a new and deeper understanding of love, through ascending Calvary. It is an opportunity for a couple to enter into a new and high process of sanctification and holiness of living. It is an opportunity to embrace the Cross of Jesus Christ. It is an opportunity to become Saints.
This is just my opinion, of course, but I somehow cannot see either St Thomas Aquinas or St Augustine, or any of the Doctors of the Church, given what they wrote, arguing for condoms in marriage, in any circumstances. If a doctor gives more morphine than usual to a patient to relieve pain but the unintended side effect is death, the doctor did not know that the outcome would certainly be death. In order to reduce suffering, he took a similar risk out of concern for his patient as a doctor who performs high risk surgery to save a human life. The situation with condoms in marital sex is different.
The intention may be good, but the outcome (as long as the condom works) is known beforehand. Because the outcomes of non-unitive sex and non-procreative sex are already known, the use of the condom cannot be excused, or morally justified because its application destroys the binary purpose of sexual intercourse in marriage. Sex, with a condom, in marriage, is not sexual intercourse, it is mutual masturbation and mutual pleasure giving that does not even lead to full union and, understood in the Tradition of the Church, sexual intercourse within marriage is nothing if it does not culminate in the full union of man and woman. The idea that 'anything goes' in marriage is quite wrong. Both the use of the condom and anal sex in marriage, are in the tradition of the Church's understanding, sins against nature, sexual acts running contrary to natural law, whether the couple are married or, indeed, not.
In other words, if a married couple find that they cannot in conscience 'go forth and multiply' or become 'one flesh' then the moral duty is to go forth and embrace the Cross of Christ. A man cannot contradict or reject his duty to reflect God's own nature of total self-giving, as exemplified by the Cross of Our Lord Jesus Christ, without going against his sacred Conscience. The condom strangles and restricts that total self-giving in the sexual act immediately and throughout the sexual act. The man is consciously aware of that one unfortunate fact and so is the woman. The man and the woman, in this painful vale of tears must, then, give themselves, in a new and sublime sacrifice, the embracing of which is a true reflection of Divine love, to God.
Contrary to popular belief, the invention and widespread use of the condom do not present the Church with a 'new dilemma'. Attempts at thwarting both the procreative and unitive purposes of sex within marriage are as old as sin itself. Neither is it true to say that potentially fatal sexually transmitted diseases constitute a purely modern phenomenon. All comments, positive or negative, on this post are gladly welcomed because whether the Supreme Pontiff meant to or not, his words, reported during an interview appear to have opened up a debate, the outcome of which, if it takes place in the highest levels of the Church, is of supreme importance to the life, health and future of the Universal Church.