Tracing some of the histories of the idea of civil war, and showing how definitions and understandings of this mode of conflict have always been volatile and contested, is the purpose of this latest book by David Armitage. Like all his work, Civil Wars: A History in Ideas is concise, wonderfully lucid, highly intelligent, and based on a confident command of a wide range of printed sources. It is also ambitious. But as he admits, it is hardly comprehensive. This is not simply because of the scale of his subject matter, but also because of his chosen methodologies.