Right now in the Vatican, a bunch of bishops are in a meeting called a synod to talk about issues related to the family. As an advisory committee to the Pope, a synod has no real power in the Catholic Church, but it is still important because of the fissures it reveals.

The flashpoint issue is whether divorced and remarried people should be allowed to receive communion. The Catholic Church believes, taking after the words of Jesus, that marriage is indissoluble, and that second marriages are adulterous. This is a very hard teaching in a Gospel full of hard teachings. It also believes that adultery is a very serious sin, and that people who are in a state of serious sin should, for their own spiritual protection, refrain from partaking in holy communion. A number of synod bishops — small in number, but well connected, and perhaps supported by Francis — want to change this historic belief.

Or at least that's what Catholics have believed for millennia. In a letter to the Church at Corinth, the Apostle Paul enjoins the Church to exclude from communion a man in serious sexual sin (in that case, incest). In the early Church, nonbelievers and people who were known to live in serious sin were welcome to church to hear the Gospel preached, but were physically escorted from the premises before communion began. The Renaissance Papacy, not exactly known for its scrupulous adherence to the words of Jesus, still preferred to cut off the Church of England and allow one of the deepest schisms in Church history — and human and cultural devastation on a grand scale at the hands of English reformers — rather than accede to King Henry VIII's request for a divorce.

So why is anybody contemplating this change?

There are all sorts of reasons. Proponents of the change note that while God's law is real, Jesus also spoke a lot about mercy. (Opponents would say that mercy at the expense of truth is no mercy at all.) And, obviously, proponents have noted that traditional Christian sexual ethics are very often a flashpoint between contemporary culture and the Church (a stumbling block, one might say), and despite the astonishing decline of Christian groups that have tried to chase after the endlessly-receding horizon of acceptable contemporary sexual norms they seem to sincerely believe that changing doctrine on this issue would help the Church. And, no doubt, they are sincerely appalled at the many difficult personal situations that this Church rule engenders — people whose first marriages are irretrievably dead and who have built beautiful second families, who want to live and pass on the faith, and yet still find themselves excluded, if not from the Church, then certainly from one of its most important rites.

Ok, but why is this such a big deal? Why is such an increasing number of Catholic pundits (including myself, a Pope Francis fan) warning about a breakup of the Catholic Church?

Another important point here, perhaps hard to grasp for non-Catholics and nonreligious people in general, is that Catholicism's own traditional self-understanding has been that its doctrines are not policy that can or should be changed depending on what's happening on the ground and what Church leaders think is best. Instead, they're a "deposit of faith," immutable doctrines handed down by Jesus, the Son of God, to his Church.

Catholics, certainly, believe in "development of doctrine," that is to say, that the Church's understanding of this unchangeable deposit grows over time, and that therefore the faith evolves. But development is not a 180-degree turn. Many issues are gray. Some are black or white, which is what this issue looks like. Either marriage is indissoluble, or it isn't. Either adultery is a serious sin, or it isn't. Either people in serious sin should receive communion, or they shouldn't.

If the Pope changed a rule that has been understood as a Catholic doctrine by seemingly every generation of Catholics up to now, it wouldn't just be the rule that would be upset — it would be Catholicism's own self-understanding.

Now, perhaps there's a smart political compromise to be made? Perhaps instead of deciding one way or another, Francis could, say, allow bishops or national bishops' bodies to decide on the rule?

In a way, and nevermind the strangeness of the idea that something can be a sin in Tulsa and not in Tangiers, that would make things even worse. Inevitably, some regions — many places in Africa, Poland — would go the conservative direction, and others would go the liberal direction, pointing to a fractured, internally divided communion, like the Anglicans. But actually things would probably be worse, because Rome would still retain its power of appeal. Conservatives in liberal jurisdictions would appeal to Rome, and vice versa. Every discussion, every debate, would become a game of high brinksmanship, with the unity of the Church on the line.

At some point, inevitably, some bishops would want to bless same-sex unions or say abortion is okay (only in some cases!), and then another group of bishops would simply refuse to be in communion with them — and the Church would be broken. Another schism.

Some say that's an outlandish suggestion, but schisms can and do indeed happen. The Church's unity never looked so strong as on the eve of the Protestant Reformation, and it's hard to say the Church's unity looks great these days. The scenario might not be the most likely, but it's certainly a plausible scenario — one that should make every Catholic blanch.

On top of their sincere belief on the merits of this issue, it is because of this fear that so many bishops at the synod, and so many Catholic writers, are increasingly tense about what is going on in Rome.

From a pure political perspective, it's hard to see how it ends. Pope Francis is widely perceived — rightly or not, I suspect only he knows — as having set up the synod to legitimate his desire to see a change of Church doctrine on this issue. But as the rebellion of most synod bishops against the proposal shows, accepting it, either directly or indirectly by punting the issue to national bishops' conferences, would lead to disaster. On the other hand, Francis might lose a lot of face — and a lot of PR goodwill — by simply folding.

Thankfully, a purely political perspective has never been enough to understand Catholicism. Hopefully, Pope Francis is not a politician, but a shepherd. My money is still on a good outcome. I guess we'll see.