"The Battle Hymn of the Republic has been one of the most effective instruments of religious nationalism since 1861 in making America and its wars sacred and therefore beyond doubt or dissent"--

Steven K. Green, renowned for his scholarship on the separation of church and state, charts the career of the concept and helps us understand how it has fallen into disfavor with many Americans. In 1802, President Thomas Jefferson distilled a leading idea in the early American republic and wrote of a wall of separation between church and state. That metaphor has come down from Jefferson to twenty-first-century Americans through a long history of jurisprudence,...