In Braintrust, Patricia Churchland sets out to synthesize and explain recent developments in the biological sciences that shed light on the nature of human morality. Churchland casts a wide net and covers a lot of ground. After a brief introduction, seven dense chapters examine a range of complex topics, including evolutionary constraints on social and moral behavior; the evolution of the mammalian brain (with particular emphasis on hormones such as oxytocin); the neurobiological basis of human cooperation (again with reference to oxytocin); the genetic blueprint for moral cognition and the evidentiary status of specialized moral modules; mirror neurons and other neurocognitive mechanisms of mental state attribution; the proper place of rules, norms, and laws in a naturalistic ethics; and religion and morality.
The treatment of these subjects is generally informative and often quite illuminating, albeit occasionally superficial. Churchland writes elegantly and presents a clear, distinctive, and forceful viewpoint on the science of morality, which draws inspiration from Aristotle, Hume, and Darwin. Her principal thesis, that moral and social values are rooted in the neurobiology of care, trust, and cooperation, deserves to be taken seriously by scientists and philosophers alike. In this review, I focus on three perceived weaknesses of Churchland’s stimulating book that likely will be of particular interest to philosophers: her interpretation of Hume, her skepticism toward innate moral principles, and her treatment of moral rules. I then conclude by making a few brief observations about the general significance of Braintrust.