Two late Victorian ideas disrupted American legal thought: the Darwinian theory of evolution and marginalist economics. The legal thought that emerged can be called 'neoclassical', because it embodied ideas that were radically new while retaining many elements of what had gone before. Although Darwinian social science was developed earlier, in most legal disciplines outside of criminal law and race theory marginalist approaches came to dominate. This book carries these themes through a variety of legal subjects in both public and private law.