Picture the scene. You’re in the zone, having a discussion you feel strongly about. Perhaps it’s your position on climate change, or your (justified) preference for dogs over cats. You deliver a passionate, beautifully constructed argument. And then you hear it: “Okay, but just playing devil’s advocate here. . .”

Of all the ways people use rhetoric, the position of devil’s advocate must be among the most frustrating. It is a title assumed by those who want to advance an argument they are unwilling to endorse outright. In theory, this can be a good thing: Our position in a debate should be decided by facts, rather than the reverse. Thus, someone with little or no personal investment in their own argument may be able to provide valuable insight. 

And, indeed, the term has l...