Herbert Spencer (1820-1903) was a major figure in the early development of sociology, famous for work which likened society to an organism and analysed it in evolutionary terms. In this context he was contributing to evolutionary theory before as well as after Darwin and argued consistently that society would be perfected through the operation of the principle that every man should be left free to do what he would as long as he did not interfere with another man's freedom. Spencer's work has been neglected in recent years, but its indirect influence lives on both in libertarian political thought and in the discipline of sociology itself particularly through the work of Durkheim who was heavily influenced by Spencer. This major set traces that influence from the reaction of Spencer's contemporaries to the present day. Contributions come from across the social science disciplines and are often taken from difficult to access contemporary sources.