Response to Eduardo

Actually, I think the fourth criterion (proportionality) listed by Eduardo is the main stumbling block.

Regarding evil effects: Even if we were to assume that there is no objective evil in avoiding pregnancy during intercourse as long as this effect is not subjectively intended (something which I doubt), there remains the complex but real evil of giving "scandal" both in the act of using a condom and in the teaching that this is permissible.

It would seem that the good effect of avoiding AIDS might still count as a proportionate reason to permit such acts, but I'm not sure that this can enter the calculus. Implicit, I think, in testing the proportionality of good and evil effects is the necessary linkage between the two. Here, since abstinence achieves the good effect of avoiding AIDS without the above-mentioned evil effects, it would seem that AIDS does not enter the double effect calculus of proportionality.

However, another good effect does enter the calculus: the good of marital relations. Particularly if we took an old-fashioned approach and called such relations a marital "duty", it would seem that the good effect of such relations might counter-balance any evil effects of scandal. But that's a very difficult empirical judgment of prudence.

Yet even if the use of a condom here were not held to be justified under double effect principles, I would think it could still count a "lesser evil". "Lesser evil" analysis, I believe, is used to justify preferring a lesser evil, where the fact that it is an evil has been made clear and where there is no realistic prospect of avoiding all evils. If abstinence is taken off the table, because spouses will insist on sex, it seems to me that the other spouse could legitimately demand or use a condom to protect herself. Even if this remains an evil, which Eduardo argues cogently it may not be, it seems to me clearly the lesser evil. The real problem comes in making these complex matters clear to the laity without causing the deep scandal of appearing to revise basic Catholic teachings.