Is Desirism An Objective Moral Theory?

Luke Muehlhauser claims that desirism is an objective moral theory. I think it’s quite easy to demonstrate that this is an incoherent claim. Recall that Luke defines “objective moral value” thus:

…usually, the phrase “OBJECTIVE moral value” means something like “moral value grounded in something beyond the attitudes of a person or persons.” Right? If what you’re calling “moral value” is just based off somebody’s personal attitudes, that’s called SUBJECTIVE morality. [The Science of Morality: No Gods Required]

Next, recall that in desirism, desires are the objects of evaluation, and that a desire is a “propositional attitude.”

Now, consider the following propositions:

A) Moral value based on personal attitudes is subjective morality;

B) Desires are the objects of evaluation in desirism;

C) Desires are propositional attitudes which vary from person to person;

D) Desirism is based off personal attitudes, hence, a subjective theory of morality.

It should be apparent that either A, B and/or C need emendations, else, D is a valid conclusion. I anticipate that Luke might respond by repeating the claim he made the first time I brought this to his attention:

…desire-based accounts of morality are not generally considered subjective when the desires being considered are all desires that exist. [Dr. Craig and Objective Morality]

What exactly does it mean to say “not generally considered subjective?” Is Luke alluding to a real-world consensus amongst the philosophical elite? Is that phrase supposed to carry some sort of weight or authority that I should assent to? Personally, I’m not concerned with what “people generally” or “philosophers generally” consider, about anything. I want to know – from Luke – how a system based on “somebody’s” attitudes is subjective, but a system based on “everybody’s” attitudes is objective.

Another rejoinder I’ve heard Luke use is the “desires of all sentient beings” distinction, but I still fail to see how this resolves the apparent contradiction. More, if a desire is a propositional attitude, is it accurate to say that all sentient creatures have desires? Further, if we answer that question in the affirmative, Lastly, what of the practical issues? Might we poll earthworms to see if we’re thwarting their desires? It seems to me that widening the scope to “all sentient creatures” simply complicates an already-complicated “theory” that proffers no numerical or technical explanation whatsoever [as an aside, desirism’s specific stance on non-human desires is hitherto unclear. Luke does appear to argue that desirism evaluates all desires that exist, which would include non-human desires – both lower animals – and any higher forms of intelligence should they exist].

At any rate, without a sound explanation for what appears to be an unavoidable conclusion, I’m going with the unavoidable conclusion: as delineated thus far, desirism cannot rightfully be called an objective theory by Luke’s current definition of objective moral value.

What do you think?