I've been thinking a bit about one of the key issues of the recent Synod on the Family, whether Catholics who have divorced and attempted remarriage without an annulment should be allowed to receive communion. As I understand the disagreement (I found this quite helpful), it's not really about the nature of marriage.
The basic case to think about is this:
Jack believes himself to be married to Jill, and publicly lives with her as husband and wife. But the Church knows, although Jack does not, that Jack is either unmarried or married to Suzy.Should Jack be allowed to receive communion? After all, Jack is committing adultery (if he is actually married to Suzy) or fornication (if he's not actually married to Suzy) with Jill, and that's public wrongdoing. However, Jack is deluded into thinking that he's actually married to Jill. So Jack isn't aware that he's committing adultery or fornication. Jack may or may not be innocent in his delusion. If he is innocent in his delusion, then he is not culpably sinning ("formally sinning", as we Catholics say) in his adultery or fornication.
This is a hard question. On the one hand, given the spiritual benefits of the Eucharist, the Church should strive to avoid denying communion to an innocent person, and Jack might be innocent. On the other hand, letting Jack receive communion reinforces his delusion of being married to Jill, making him think that all is well with this aspect of his life, and committing adultery and fornication is good neither for Jack nor for Jill, even if they are ignorant of the fact that their relationship is adulterous or fornicatory.
One thing should be clear: this is not a clear case. There really are serious considerations in both directions, considerations fully faithful to the teaching of Scripture and Tradition that adultery and fornication are gravely wrong and that one should not receive communion when one is guilty of grave wrong.
One may think that the above way of spinning the case is not a fair reflection of real-world divorce and remarriage cases. What I said above makes it sound like Jack has hallucinated a wedding with Jill and may have amnesia about a wedding with Suzy. And indeed it is a difficult and far from clear pastoral question what to do with congregants who are suffering from hallucinations and amnesia. But in the real-life cases under debate, Jack really does remember exchanging vows with Suzy, and yet he has later exchanged other vows, in a non-Catholic ceremony, with Jill. Moreover, Jack knows that the Church teaches things that imply that he isn't really married to Jill. Does this make the basic case clear?
Well, to fill out the case, we also need to add the further information that the culture, at both the popular and elite levels, is telling Jack that he is married to Jill. And Jack thinks that the Church is wrong and the culture is right. I doubt we can draw a bright line between cases of mental aberration and those of being misled by the opinions of others. We are social animals, after all. (If "everyone" were to tell me that I never had a PhD thesis defense, I would start doubting my memories.)
At the same time, the cultural point plays in two opposite ways. On the one hand, it makes it more likely that Jack's ignorance is not culpable. On the other hand, it makes it imperative--not just for Jack and Jill's sake, but now also that of many others--not to act in ways that reinforce the ignorance and delusion. Moreover, the issue for Jack's spiritual health isn't just about his relationship with Jill. If Jack puts more weight in the culture than in Catholic teaching, Jack has other problems, and may need a serious jolt. But even that's not clear: that jolt might push him even further away from where he should be.
So I don't really know what the Church should do, and I hope the Holy Spirit will guide Pope Francis to act wisely.
In any case, I think my point stands that this isn't really about the nature of marriage. One can have complete agreement that adultery and fornication are wrong and that Jack isn't married to Jill, without it being clear what to do.