A Question about Moral Disagreements

Often, when reading discussions of moral disagreements and what we should think about them, I come across a claim like the following: Even if it turns out that quite a few moral disagreements result from disagreements about the non-moral facts, it's clear that some moral disagreements would remain even if people agreed about the non-moral facts.

Now, I assume that, though this is usually how the point is put, something more is being claimed here. It's not just that people would continue to disagree about moral issues while agreeing about all non-moral ones, but that they would continue disagree in these situations even in cases where the parties aren't making an errors in their reasoning. For these moral disagreements wouldn't be so troubling if they resulted from failing to fully understand the facts one know, to grasp their logical implications, etc. So we're also supposed to be imagining cases in which people make no errors in reasoning and fully appreciate the facts they know and so forth. And I suppose we should also rule out things like bias and the like here.

Furthermore, it also seems that the continued existence of such disagreement would be an interesting fact only if we assume that people also have some (or all?) of the information that would be relevant in coming to conclusions about the moral issues they disagree about. Even if two people have all the same beliefs about the non-moral facts, it wouldn't be too surprising that they reached different moral conclusions if their beliefs weren't the ones that were relevant to discovering the moral facts they disagreed about. So maybe we need to make the claim one about the continued disagreement between people who have all the non-moral facts or at least all the relevant non-moral facts. Let's restrict it to people who have all the relevant non-moral facts, as this is somewhat easier to conceive--and maybe we also have real cases of this. (I'm not sure we have any idea whether people would continue to disagree if they had absolutely all non-moral facts--and I'm pretty sure that no one has all those facts.)

I'm probably forgetting some additional qualifications here, but let's get to the point.

All right, so we're supposed to imagine people who agree about all the relevant non-moral facts, who don't make any errors in reasoning, who fully appreciate the relevant facts, and who aren't biased. Will such people still disagree about moral issues? It's supposed to be obvious that, at least in some cases, they will; but I've never found this all that obvious. I'm not sure that it's false--indeed, it has some prima facie plausibility--but it's far from obvious to me.

And I'm wondering what other people think about this. Is it obvious to you? And if so, why?

I can think of a couple arguments for the conclusion that such people would still disagree. I'm not sure what to think of either of them.

The first argument is pretty simple. It claims that we have some actual cases where people have all the relevant non-moral evidence and yet disagree. So this isn't something we have to imagine; it actually exists. Surely, that would be a good argument. But are there such cases? A case people often appeal to is one having to do with abortion. The idea is supposed to be that there are cases in which people with different views about the permissibility of a particular abortion know all there is to know about the development of the fetus and so forth. I don't know what to think about this sort of argument. But it's not obviously compelling. There are a couple of problems here. First, it's not really clear that cases like this are cases in which we have agreement about all the relevant facts. For disputes about abortion often turn on disputes about metaphysical and religious issues, and so it's not clear that there are all that many disagreements in which people agree about all the relevant facts. Now, of course, not all the moral disagreement about abortion reduces to this. There are, for instance, cases of atheists who disagree about abortion, and perhaps there are even such cases where the people agree about all the other relevant facts. Maybe. It's very hard to tell since it's hard to tell just what all the relevant facts are, and this brings us to the second problem here. How are we really supposed to determine whether we've got people who agree about all the relevant facts? This would seem to require appealing to some contentious issues in normative ethics, and so it's not altogether clear that we've actually got the sort of cases we're looking for. OK, enough of that.

The second argument is going to have to be more complex. Rather than pointing to cases in which people have all the relevant non-moral evidence, it appeals to more everyday cases of moral disagreement. The idea here is to argue that ordinary moral argument doesn't proceed in a way that suggests that agreement about all the non-moral facts will lead to agreement about the moral facts. So the main premise here is that moral positions are not responsive to additional non-moral facts in the way we would expect them to be if full non-moral information would lead to convergence of moral opinions. Is this true? I leave it up to the reader to decide.

I'm sure there are other arguments that some moral disagreement will persist even if people possess all the relevant non-moral information. But I'm not sure what they are. Can anybody give me some, or tell me how I've underestimated the plausibility of these other arguments?