Hunting Down Social Darwinism is the third and final installment in the trilogy, The Nature of Liberty. The trilogy gives a secular, ethical defense of laissez-faire capitalism, inspired by Ayn Rand's ideas. The trilogy's first book, The Freedom of Peaceful Action, provided the philosophic theory behind the ethics of a free-enterprise system based on the individual rights to life, liberty, and private property which John Locke described. The second installment, Life in the Market Ecosystem, explained how free enterprise functions much as a natural ecosystem wherein behavioral norms develop, bottom-up, from repeat interactions among individual participants in the economy.

As such defenses of free enterprise are frequently criticized as "social Darwinism," however, this third and final installment of the trilogy asks the question, "What is social Darwinism?" The book embarks on a hunt for the term's meaning, explores social Darwinism's beginnings, and examines whether it is fair to describe such nineteenth-century free-market advocates as Herbert Spencer and William Graham Sumner as social Darwinists. It then addresses the accusation that the free-market Darwinism commonly ascribed to Spencer and Sumner rationalized bigotry and founded the pseudoscience of eugenics. In the process, the book refutes various myths about the topic popularized by such scholars as Richard Hofstadter and John Kenneth Galbraith.

The extent to which the popular narratives about social Darwinism prove to be inaccurate holds enormous ramifications for current controversies. It has implications for debates over the ethical appropriateness of reducing taxpayer spending on social welfare programs, and also sheds new light on the pros and cons of attempts to apply biological evolutionary theory to the study of human social institutions. Additionally discussed is the manner in which various prominent figures in economics, evolutionary psychology, and Complexity Theory have grown famous for advancing ideas which Spencer and Sumner originated, even as such figures simultaneously downplay the importance of Spencer and Sumner to their field. Following the hunt for social Darwinism, this work sums up the trilogy with some final thoughts on the importance that liberty holds for every effort to live life to the fullest.