In explaining why two reasonable people can so seldom cross the divide of religious or political or intellectual difference, he provided this unsettling but profoundly powerful insight: “As reasoning is not the source, whence either disputant derives his tenets; it is in vain to expect, that any logic, which speaks not to the affections, will ever engage him to embrace sounder principles.”15 Hume made of this insight a principle that seems most unphilosophical: “Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.”
