So I was wondering, if one spouse knows that his/her spouse is using a contraception, and has sex anyway, is she guilty of a mortal sin as well as the spouse who is using it?
Passive co-operation in “withdrawal” can be licit for serious reasons, since the marital act in that case is (as far as the external act is concerned) licit up until the withdrawal actually happens. OTOH, if barrier contraception is used then such co-operation would not be licit, since such an act is evil from its beginning. I am not sure how this would apply to chemical forms of contraception.
Catholic Answers once had a caller, who raised that a male friend’s wife started using birth control and whilst he was against it, he couldn’t prevent her from taking it and it was causing marital strife.
It was discussed, and IIRC, it was her sin. And so not cause more marital strife, they could still be intimate with each other. However, he was encourage to pray, perhaps seek counselling with his wife, and to not continuously raise it and only discuss it when she would be open to a constructive discussion.
Now, if the roles were reversed—a man uses a condom against his wife’s wishes—I’d assume that it would be similar. The other spouse knows the union wouldn’t be fruitful, however it isn’t their sin, the wife raises not using condoms at opportune moments, and they continue to be intimate as not to “rock” the boat any further.
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