This book shows how Darwinian biology supports an Aristotelian view of ethics as rooted in human nature. Defending a conception of "Darwinian natural right" based on the claim that the good is the desirable, the author argues that there are at least twenty natural desires that are universal to all human societies because they are based in human biology. The satisfaction of these natural desires constitutes a universal standard for judging social practice as either fulfilling or frustrating human nature, although prudence is required in judging what is best for particular circumstances.

The author studies the familial bonding of parents and children and the conjugal bonding of men and women as illustrating social behavior that conforms to Darwinian natural right. He also studies slavery and psychopathy as illustrating social behavior that contradicts Darwinian natural right. He argues as well that the natural moral sense does not require religious belief, although such belief can sometimes reinforce the dictates of nature.