'P. S. O'Hegarty (1879-1955)' provides an informative and lively biography of the Irish nationalist P.S. O'Hegarty, a major historical figure in the modern separatist movement. At the same time the book explores important issues within nationalism and Irish history, such as what is meant by 'nation' and national identity, cultural and political tolerance, Republican Liberalism, and the nature (as well as the clash) of religion and state.