Hang on, the original poster is still legally married. For all we know the marriage is also sacramental under church law. And for all we know the Catholic party also has a previously existing valid marriage.
Even if only the first circumstance is the case, under church law ANY marriage, Catholic or not, is presumed to be valid until such time as it is investigated by the marriage tribunal and declared not to be valid.
And yes, any person who sleeps with another prior to receiving a declaration that their marriage is invalid IS committing the sin of adultery.
And what does Our Lord say in scripture? ‘Any man who marries a divorced woman commits ADULTERY with her’. Not fornication. So it would appear any sin against marital vows, whether they be your own or the vows of your partner, would constitute adultery under Our Lord’s definition, and thus break the commandment.
Besides which, he is worried, as any good Christian should be, about the fact that YOU would be breaking the commandment for certain. Surely a Christian should be worried about the souls of others and not just their own?
kage_ar, you have it totally backwards. The poster is non-Catholic, she is married and wants to break her vows. Her boyfriend, who is Catholic, is the one who doesn’t want to do so. So he isn’t lying to get her into the sack - on the contrary he DOESN’T want to have sex with her and is trying to tell her why!