Moral Explanation?

Is it true that killing is bad? Or is there a fact of the matter? Many of us like to think so, yet we can't really describe what this fact consists in. Somehow, a state of affairs, a collection of stuff, is normative. A main motivation being a moral realism is the accompanying power of explanation. Why do I think Hitler is bad? Because he really was a horrible person.

I recently came across a fascinating article by Gilbert Harmen, who points out an asymmetry between scientific and moral explanation. Harmen asks us to consider a scientists who is conducting an experiment. She is working with a theory that predicts that she will see some phenomenon X in her cloud chamber. Now, if she looks in her cloud chamber and does see what the theory predicted, then her theory being true would explain why she saw what she saw.

Harmen then asks us to consider seeing a group of boys doing a horrible thing: burning a cat for fun. He says that most people would have something like a `moral observation' where we just see this as bad. Now, let's say we have a theory, a moral theory, under which it is a fact that burning cats is bad. But it being true that burning cats is bad doesn't really seem to explain why we would have the `moral observation' we have. The reason why we think this is bad, the explanation of why we think cat burning is bad, has to do with the way we were raised, facts about our psychology and how we were brought up. So, Harmen alleges, even if there were moral facts, it is not clear that they would take part in explanation, they way we think scientific facts do.

I don't know what to think of this. My first reaction is that it can't be that big a blow against realism. One possible way around is the Platonist route. There can be moral facts, but they are not knowable empirically but rather through some kind of rational moral intuition (like a Kantian picture with reflection on maxims or something). Or moral truths are self-evident. The other way to go is to simply deny Harmen's claim that moral truths can't explain why we have certain moral observations. Why can't they? Harmen seems to just help himself to the fact that the explanation of why we feel the ways we do must come only from psychology. But why can't moral facts supervene on physical states in a way our psychology is sensitive to?