This rich and provocative study is the first to examine Herbert Spencer's critical role in the development of liberal utilitarian moral and political philosophy in the nineteenth century, as well as the success of his version of it. While several scholars correctly see Mill as a founder of liberal utilitarianism, none have appreciated Spencer's equally important formative role. Weinstein reinterprets Spencer's version of liberal utilitarianism and illustrates that his moral and political thought exhibits greater systematic integrity than received views of his thought acknowledge.