Every once in a while, I force myself to take seriously the idea that morality, and moral disputes, are a matter of objective fact. I confess that I have never been able to find a good argument for this viewpoint, and while I know that many have been convinced by it, I confess my blindness for how.
The most convincing argument for me against the possibility that morality is about objective fact is the idea that the only "thing" we have to measure the "correctness" of moral statements by is our moral sentiments. Further, there is simply no good reason to suspect, and every reason to reject, that these are objective in nature. In other words, we have no objective moral blueprint to hold up to our moraal judgments to help us know whether they are correct. We only have our individual sentiments on the matter, which seem far from being objective.
To put the matter concretely, when two or more people disagree on a scientific proposition or conjecture, experiments can be performed (and it is quite hard to deny that the world these experiments are performed in is not objective). Competing theories will stand or fall based on their results in experiment against an objective world, results that are independent of anyone's wishes or desires.
Contrast that with disagreement over moral matters. When two people disagree on moral matters - one says x is right and the other, that x is wrong - there is nothing resemblinng the objective world - a world of moral fact- that we can hold the competing judgments up to. IN order to know whether x is REALLY right or wrong, we would have to have access to the world of moral facts, so that we can find out which proclamation that world endorses. So far as we can tell, there is no such world of moral facts (and when people say there is, they are generally getting there by intution, begging the question of how objective those intutions really are.)
Some diagree with this; they suggest that there IS a factual resolution to moral disputes. When I say x is wrong and you say x is right, some say that we can experiment. Per Hume's is/ought dichotomy, it is a different thing to say, "x causes suffering," than it is to say, "x is wrong." That x may cause suffering is an observable fact. That x is wrong expresses more than that x causes suffering, but goes further by inserting a value judgment that suffering is wrong. As good as that may sound, there is no objective way to prove the latter as there is the former. This is precisely because "x causes suffering," can be validated solely by appealing to the objective world of descriptive fact. That x is wrong is unprovable because it goes beyond the brute world of descriptive fact.
I confess that I cannot see how to get around this. The arguments I've heard seem to mistake the speaker's strong intuitional moral sense for an objective world of moral facts. And to me, there seems no good reason to suppose that these intuitions are anything more than psychological preferences (that we mistake solely becuase they are so strong that they SEEM to be obvious to everyone).
I have tried and tried to "get into the belief" and understand how one can believe in an objective morality, but there seem too many problems to make such a belief worthwhile. How can moral disagreements be resolved similarly to the objective resolutions in science? Where are the incontestible proofs of some moral propositions over others? How can "is" (recognition of fact) lead inexoribly to "ought (a prescriptive obligation)?