When I posted about this the other day, it was in a very preliminary manner, since I had not even read Michael Ruse's post in response to an earlier one by me.
Ruse puts a view that seems to me to have some points in its favour, and he concedes that it may, formally, make him a moral error theorist. I can't quite see how his view allows (as he thinks it does) for absolute (in some sense) moral truths that cannot be discovered through science but only in some other way. And exactly what this way might be has been left mysterious - is it some sort of process of conceptual analysis? Is it openness to the insights to be found in myth and literature? Or what? Still, the general view is one that at least seems to be arguable on its merits.
I've made a couple of comments on the thread, and I do have a bit more to say on the thread when I get a moment. I continue to have some problems with the overall theory, at least in the form that Ruse has developed so far. But I'm not so out of sympathy with his approach as to think that discussion and clarification is useless. (OTOH, I wonder whether he is planning to engage his commenters at all ... since he hasn't as yet. Oh well.)
On thing that does strike me as strange is that Ruse seems, if I follow him, to think that there are moral absolutes for us, though not absolutes simpliciter. As far as I can work out, these absolutes are bedrock psychological features that human beings all share, and which are basically non-negotiable (even if some rational but non-human creature did not share them, and was not making a mistake about the world in not doing so). Okay, that's possible, I suppose, if we bracket off a small class of exceptions such as psychopaths ... but how plausible is, it given the wide variety of moral views that we actually see if we study the historical and anthropological record? It looks from here as if any evolved human psychology that we all share is going to be, to say the least, rather "thin" or minimalist.
And even if I'm wrong on this - even if there is some more substantial and rich evolved human psychology, how do we know this? The humanities might be of some help, I suppose - e.g. scouring for information about old or strange cultures might reveal clues about a transcultural human nature - but isn't this sort of question primarily a matter for science, in particular psychology? In which case, how are moral truths a good example of the epistemic power of science being limited? That was, remember, Ruse's initial claim.
I don't see how Ruse can go on using supposed moral absolutes, or objective moral truths, as an example - or at least as a clear-cut one - of things that the humanities can find out but the sciences can't. At best (and I'm happy to accept this scenario) it's a situation where scientists, humanist scholars, and philosophers who have some comfort with both the wider humanities and the sciences, should cooperate to get a clearer picture of human nature and of how it feeds into human moral systems.