Ms. Churchland is an eliminative materialist who believes that nothing exists that's not reducible to its material components. Thus, for her, mind is simply a word we use to describe how the function of the material brain, just as we use "digestion" to describe the function of the stomach. There are no mental substances as such, in her world, only chemical reactions occurring in the brain.
In Conscience, according to Stark, she undertakes to analyze the origins of human morality and to explain it in terms of these neurobiological brain processes. Here's Stark:
At the core of her argument is the claim that morality is rooted in neurobiology. Pleasure-causing brain chemicals, among them oxytocin and dopamine, get released by evolutionarily adaptable activities such as mother-child bonding, in-group caring and the praise earned by cooperating with others. Such conduct, she says, comprises the common building blocks of moral behavior....Set aside the breezy, magical, wave-of-the-wand view of the evolutionary deus ex machina that's always available to materialists to solve every survival difficulty and need. The deeper problem with Ms. Churchland's view of morality is that although it may explain why we have moral feelings or sentiments, it completely empties the notion of right and wrong of any substantive meaning.
A tribal culture will define in-group caring differently from a cosmopolitan one, but in either case the moral codes developed will take root because they activate the pleasurable brain chemicals that have evolved to be stimulated by concern for others....
In Ms. Churchland's view, morality ... is the scaffold of rules that, if we observe them, elicit the pleasurable brain chemicals that evolved to encourage behavior suited to the survival of the species.
If one's behavior is a result of chemical reactions in the brain in what sense is any behavior morally wrong? If Joe gets pleasure from acting selfishly why is his selfishness wrong? If Frank gets pleasure from molesting children or raping women why is he morally wrong to engage in these behaviors?
Stark adverts briefly to the problem when he writes that,
If what distinguishes moral from immoral behavior is that the one activates pleasure-causing chemicals and the other pain-inducing chemicals... there would no longer be anything that distinguished good from bad.The behavior that brings pleasure to one person may bring pain to another. All we can say about what Joe and Frank are doing is that they're engaging in behavior that others don't like, but we can't say that their behavior is immoral. Society may make it illegal, but it can't make it immoral.
Only a transcendent moral authority can do that, and Ms. Churchland doesn't believe there are any such entities.
Thus, she seems to be stuck trying to explain morality while bereft of any sound basis for right and wrong or good and bad. Hers is, I think, a quixotic task.
Any attempt to derive an ethics based on naturalistic, materialistic presuppositions is doomed to fail. It leads to moral subjectivism which leads ultimately to moral nihilism, the view that there's actually nothing that's morally wrong. There are just things that people do.
The nihilist simply takes materialism to its logical conclusion which is that the set of behaviors labeled "moral wrongs" is a null set.
