A new draft paper on-line at SSRN; the abstract:

I revisit, refine and defend an inference to the best explanation (IBE) argument for anti-realism about reasons for acting based on the history of intractable disagreement in moral philosophy. The four key premises of the argument are: 1. If there were objective reasons for action, epistemically-well-situated observers would eventually converge upon them after two thousand years; 2. Contemporary philosophers, as the beneficiaries of two thousand years of philosophy, are epistemically well-situated observers; 3. Contemporary philosophers have not converged upon reasons for action; 4. Conclusion: there are no objective reasons for action (IBE from the first three premises). The key premises of the IBE are (1) sentimentalism; (2) non-cognitivism about basic affects; and (3) philosophical arguments for what our reasons for action are always involve a premise that depends on a basic intuitive moral judgment (that can be explained in terms of a basic non-cognitive affect). All these premises are explored in detail, and various objections addressed.

 Comments welcome from those who work on these issues; this version will be presented at a conference in Rome in September, and I won't undertake revisions until after that.