In a very nicely constructed recent paper ("Are ethical judgments intrinsically motivational? Lessons from 'acquired sociopathy'", Philosophical Psychology 16 (2003),) Adina Roskies offers a compelling argument against the position she dubs "motive internalism" (others have called it "belief internalism" or "judgment internalism"). Motive internalism states:
If an agent believes that it is right to A in circumstances C, then he is motivated to A in C.
Roskies' strategy is simple enough: She points to examples of agents for whom motive internalism is false.
Roskies discusses findings from studies of those with injuries to the ventromedial (VM) prefrontal cortex, an area of the brain widely believed to influence perception, reasoning, and emotional control. These patients perform normally on most all cognitive metrics, but have difficulty conforming to social expectations, and in particular, they seem not to act in accordance with their own sincerely held moral judgments. Roskies notes that there is no evidence of a defect of reasoning or perception, nor do patients with VM injuries lose their comprehension of moral concepts. Those with VM damage report low emotional response and affect in those contexts that ordinarily produce characteristically moral emotions (guilt, etc.), and physiologically, the VM patients do not produce the skin-conductance response (SCR) thought to correlate with the emotional or affective responses associated with moral judgments. Nevertheless, the VM patients sincerely affirm commonplace moral judgments. Roskies therefore proposes that VM patients fail to be motivated by their own moral beliefs (not even to the minimal degree that those beliefs are overridden by other motives such that guilt, regret or other reactive attidues occur when they act contrary to those beliefs). VM patients, she concludes, are counterexamples to motive internalism.
Roskies' paper is careful, and she addresses several objections that defenders of motive internalism might make to her thesis. But I'd like to consider an objection Roskies does not mention: Simply enough, the VM patients are not counterexamples to motive internalism because they do not actually possess the moral beliefs that (allegedly) fail to motivate them.
Now, I am far from an expert on belief attribution and the array of semantic, psychological, and epistemological issues it raises. But to my understanding, a wide spectrum of theories about the nature of belief would endorse the claim that an agent does not believe that P unless she behaves as a person who believes that P characteristically behaves, where the behavior in question is not only linguistic. Such a claim would be endorsed by 'dispositionalist' or 'functionalist' theories of belief, and need not contradict representationalist theories of belief either. Intuitively, it seems right to say that, e.g., a person who believes that water is deadly poison must behave as we would expect a person who believes that water is deadly poison would behave, to wit, she would probably suffer frequent dehydration and have a hysterical fear of rainstorms. (Caution is needed here: How such a person would behave is determined by a good deal else besides the belief in question, including desires and her other beliefs. But it seems at least in principle possible to isolate the role that a given belief plays in a person's overall pattern of behavior.)
So in the case of the patients with VM damage, cannot a plausible case be made that they do not have the relevant moral beliefs, as evidenced by the fact that those beliefs do not motivate them? Could there be better evidence of their not believing these moral statements than the very fact that they do not behave (nor do they seem to have the causal psychological and physiological antecedents of those who do behave) in accordance with their supposed moral beliefs?