In the past several years, the rise of the radical right and the spread of Euroskepticism, and, more recently, the vote in favor of a British exit from the EU, have focused attention on the cultural and ideological sources of support for and opposition to European integration. This book focuses on religion, and in particular the split between Catholics and Protestants, which was perhaps the most important division at the time that integration began in the 1950s. Nelsen and Guth revive the notion, once widely held by historians, that Catholics naturally favor integration whereas Protestants naturally oppose it. There are many reasons why one might think this is so, but the authors emphasize how current political attitudes are rooted in the battles of the Reformation era. Ever since that period, Catholics have viewed Europe, favorably, as fostering a single universal culture that transcends nation-states, whereas Protestants have seen the nation-state as an essential bulwark against just that sort of universalism, which they tend to fear. The book’s historical and statistical analysis is more suggestive than conclusive, and it fails to demonstrate that any correlation between Catholicism and pro-European sentiments results from the cultural factors the authors highlight. Yet it is nonetheless a provocative and original analysis that might help launch further debate on the historical origins of today’s conflicts over the EU.