My Sunday column used the double canonization of two of his predecessors to discuss some of the perils awaiting Pope Francis as his pontificate advances, and it concluded with a fairly stark claim: Some of the proposals on divorce, remarriage and communion that have been put forward by prominent figures in the church, I wrote, might lead to schism if the pope were to adopt and implement them.

This no doubt sounded a bit overheated to many readers, so I think further explanation is in order. (Warning: Catholic inside baseball below.)

The Catholic Church’s teaching on marriage is often mischaracterized, but here’s a brief, probably-incomplete attempt at explanation. Following the words of Jesus and its own longstanding traditions, the church holds that valid sacramental marriages — that is, between two baptized Christians — are inherently indissoluble, meaning that in such circumstances a second marriage is (from the Catholic perspective) an impossibility, and Catholics who remarry after a civil divorce are actually committing the sin of adultery. This, in turn, has implications for the reception of communion, which is not supposed to take place if an individual is persisting in grave sin: A divorced Catholic can receive communion (so long as they aren’t responsible for abandoning a spouse who wants them to return, or engaged in some other form of grave, unrepented sin), but a divorced-and-remarried Catholic should not, unless they intend to live with their new spouse as brother and sister instead of man and wife.

Now: This strict teaching coexists with a less strict — and potentially much less strict — definition of what constitutes a valid marriage. Historically, Catholic marriages could be annulled (that is, declared to have been invalid from the beginning) for a fairly narrow range of reasons — a failure to consummate the union, consanguinity, the existence of a previous marriage, etc. But in recent decades, especially in the frequently-divorcing West, the range of justifications for annulling a marriage has expanded to include a much larger range of factors, psychological and emotional and intellectual, which might demonstrate that one or both members of a couple entering into a marriage basically didn’t understand what they were getting into, didn’t have a fully Christian understanding of the sacrament or fully Christian intentions to live it out, and thus weren’t capable of the kind of true consent that a true marriage definitionally requires. And the (incorrect, but understandable) popular view of the annulment process as a kind of “Catholic divorce” flows from this more expansive list of reasons why a marriage might be declared null and void, and from the more expansive consequences: The United States, ground zero for the approach, has 6 percent of the world’s Catholics and about 60 percent of the world’s annulments.

Not surprisingly, the wisdom of this expansive approach is vigorously debated within the church. It’s been defended on the grounds that with the weakening of Christianity in Western culture and the apparent failure of Catholic catechesis among the young, modern couples really are much more likely to enter into sacramental marriages without really understanding what they’re doing; it’s been criticized as reflecting a kind of “anthropological pessimism” that understates “the innate human capacity to marry” even in cultural contexts unfriendly to the institution.

But the debate notwithstanding, nobody denies that an annulment process of some kind is compatible with the traditional Catholic view of marriage’s indissolubility, and I think that most critics of the American way of annulment would concede that a form that considers psychological and cultural factors, while prone to practical abuses, doesn’t introduce any inherent logical tensions into the church’s teaching on marriage. (There’s also no question that in a multi-religious society where people move more often between faiths, situations that were once rare — Google “Pauline Privilege” for an example — are likely to become more commonplace, and church rubrics need to become more flexible to deal with them.)

So the church has a certain amount of room to change its policies and practices (whether wisely or not; I’m bracketing that issue) on annulments without necessarily calling doctrine into question. If, for instance, following next year’s synod of bishops (which is focused on family life), Pope Francis were to take steps to expand, alter and streamline the annulment process in ways that might ultimately bring American-style annulment rates to other parts of of the Catholic world — well, there would undoubtedly be criticism and lively argument about the wisdom of the move, but it wouldn’t create a theological crisis for Catholic conservatives, or call into question the authority of his office.

However, what’s being proposed and discussed and debated among some of the church’s bishops and cardinals — with, it would seem, the blessing of the pope — is something significantly different: An official mechanism whereby a divorced and remarried Catholic could, without having their previous marriage declared invalid, do penance for any sins involved in their divorce and then receive communion without their new marriage being a moral impediment to reception of the host. In practice, this would move the church in the direction of Eastern Orthodoxy, which has traditionally allowed pastoral exceptions for second marriages, but it would so in a more ambiguous way — effectively creating a kind of second tier of marital unions for Catholics, whose existence the church would decide to “tolerate” (in the words of Cardinal Walter Kasper, the leading voice making the proposal) but “not accept.”

Now one can debate the practical effects of such a proposal (I have various thoughts, but again, I’ll save them). And one certainly can, as the Orthodox and many Protestant churches do, make reasonable theological and biblical arguments for accepting second marriages in some form. But here’s the crucial problem: The test for changes to Catholic practice isn’t just supposed to be “what practical consequences are likely to ensue?” and the bar that such changes need to clear isn’t just supposed to be “what can be reasonably defended by thoughtful Christians?” Rather, the primary test and crucial bar alike are supposed to be “what can be reasonably defended in the light of what the Roman Catholic Church has historically affirmed and taught?”

Seen in that light, it is very hard for me to understand how this kind of change wouldn’t create some pretty significant internal problems for Catholic doctrine as currently and traditionally understood. Saying, with Cardinal Kasper, that second marriages can be tolerated but not accepted implies a zone of human conduct that one might call “tolerable sinfulness,” which is an idea that church teaching does not currently support. (And which if it did support would have all kinds of moral and doctrinal implications, extending well beyond this particular debate.) And whatever individuals and pastors decide to take upon their own consciences, declaring the reception of communion licit for the remarried-but-not-annulled in any systematic way seems impossible without real changes — each with its own potential doctrinal ripples — to one or more of three theologically-important Catholic ideas: The understanding that people in grave sin should not generally receive the Eucharist, the understanding that adultery is always a grave sin, and/or the understanding that a valid sacramental marriage is indissoluble.

Which in turn would mean that if he actually made this kind of change — and, as I said in the column, I do not think he will, but it is being debated with his apparent encouragement, so the possibility has to be addressed — Pope Francis would be either dissolving important church teachings into what looks to me like incoherence, or else changing those same teachings in a way that many conservative Catholics believe that the pope simply cannot do.

Now I am obviously neither a theologian nor a church historian, so my judgments on an issue like this are hardly (ahem) infallible. But in following the controversy, the arguments that this sort of move would not require a doctrinal change seem fairly weak. There is the claim that it would be a strictly disciplinary change, not a dogmatic one … but unlike many other disciplinary issues (from Friday fasts to priestly celibacy), this seems like a case where the discipline is more or less required by a doctrine or doctrines, and to alter one is to at least strongly imply an alteration in the others. There is also the invocation of practices from the early centuries of the church, when some second marriages may have been handled in this manner, and the suggestion that under such a reform the church would be simply returning to an ancient practice. But the entire theory of the development of dogma, which is central to defenses of continuity in Catholic teaching, would seem to militate against the idea that the consistent witness (and to this layman, it really does look pretty consistent) of the second millennium of Catholic history, complete with martyrs and dogmatic definitions, can safely be set aside because of some highly ambiguous cases from the first millennium.

Now these are not points that would trouble many liberal Catholics, who often reject the intertwined ideas of consistency in Catholic doctrine and papal infallibility, and for whom the idea of a pope willing to alter doctrine might be a consummation devoutly to be wished. But for conservative Catholics, many of whom have spent the John Paul and Benedict eras arguing that on a range of controversial questions the whole issue isn’t just that the church shouldn’t change, but that it can’t … well, if a change like this did happen, however hedged and with however many first millennium antecedents invoked, that conservative argument would at the very least look weaker than it did during the last two pontificates.

And since it isn’t a small argument … since the church’s claim to a constant, non-contradicting authority lies close to the heart of why many conservative Catholics are conservative Catholics … well, that’s why the “schism” possibility seems worth raising, because hard-to-process theological shocks are where institutional fractures often start. It’s one thing for conservative Catholics to serve as a kind of loyal opposition during this pontificate — to learn to doubt a pope, or disagree with his rhetoric or decision-making, while remaining faithful to the office and the church. It’s quite another if one of those papal decisions seriously calls into question the doctrinal continuity that’s the very root of conservative-Catholic loyalty. And there just isn’t a recent model apart from the Lefebvrist schism for how that kind of more-Catholic-than-the-pope dissent would practically work.

But once again, I could be completely wrong, about either the problematic nature of the shift being discussed or the likely conservative reaction to the change. All I can say for certain is that a development like this would leave me more doubtful than before about the consistency of Catholic doctrine and the nature of the church. But I’m not sure what to read into these feelings: While I obviously fall into the conservative camp in the Catholic culture wars I’m also on the less-rigorous, more-latitudinarian end of the conservative-Catholic spectrum, so I tend to expect that what unsettles me should unsettle the more rigorous even more … but it could also be that if I were more rigorous I’d be more trusting and less suspicious, and less likely to see (invent?) discontinuities where they might not actually exist. I’m not sure …

… But I am sure that I’ve said enough here, so I’ll leave off. Interesting times. Ora pro nobis.