One hundred fifty-five years ago, the Atlantic Monthly published on its front cover the lyrics to “The Battle Hymn of the Republic,” which not only is one of this nation’s most well-known patriot songs, but also, arguably, its most spiritual. The melody was borrowed from a Civil War marching song, which paid tribute to the abolitionist John Brown, and which was popular with Union soldiers. The song’s lyrics – “poor old John Brown is dead, his body lies mouldering in the grave” – were inoffensive to soldiers marching into battle, but deemed too coarse to be sung by the general...