Prominent historian Mark Noll considers the Civil War as a major turning point in American religious thought, as both Northerners and Southerners generally agreed on the authority of the Bible but disagreed about what it taught about slavery. He also surveys the observations of foreign Protestants and Catholics, who saw clearly that regardless of how much voluntary reliance on scriptural authority had contributed to the construction of national civilization, if there were no higher religious authority than the personal interpretation of scripture, public deadlock over conflicting interpretations would amount to a full-blown theological crisis.