Richard,

Until persuaded otherwise, I agree with you on this point. (These days, I take Richard Joyce to have the clearest defense of error theory, and I just subtract his confusing-to-me defense of fictionalism.) Besides, I think there are better ways of getting something like an 'objective' ethical theory (in something like a 'realist' sense) while still holding that reasons for action arise only from desires, or from relations between desires and states of affairs. In fact, that's the kind of theory I defend: desirism. Though, I'm not too interested anymore in whether desirism is to be called 'objective' or 'realist', even though I think a good case can be made for both.