"One hundred and sixty years ago F. C. Baur posed, in inescapably sharp form, a question which has haunted Christianity throughout its history: is Christianity simply a form of Judaism, development from Judaism, or was it, as Baur argued, from the beginning something quite distinct, a religious spirit or consciousness which could not be or become itself until it broke through the limits and restrictions of its historical origins? Baur's radical answer set the agenda for the rest of the nineteenth century, and though neglected for most of the twentieth century, the question has reemerged with...