Mill states it well: "He who knows only his own side of the case knows little of that." If someone can correctly explain a position but continue to disagree with it, that position is less likely to be correct. And if ability to correctly explain a position leads almost automatically to agreement with it, that position is more likely to be correct.
[...] Put me and five random liberal social science Ph.D.s in a chat room. Let liberal readers ask questions for an hour, then vote on who isn't really a liberal. Then put Krugman and five random libertarian social science Ph.D.s in a chat room. Let libertarian readers ask questions for an hour, then vote on who isn't really a libertarian. Simple as that.
My challenge: Nail down the logistics, and I'll happily bet money that I fool more voters than Krugman.
Just like Caplan, I'd like to put my money where my mouth is and play in an ideological Turing Test against a Christian blogger.
UPDATE: Two Christians have contacted me to tell me they're interested. Please suggest format ideas for us to talk over and let me know if you'd like to join in!
update to clarify: When the panel is made up of mostly genuine Blues and one or a few Greens pretending to be Blue, then the judges are all Blue.
This seems like a very fun game, but I'm not sure how much merit it has as a method of determining which side in a debate is the most informed.
Much like the actual Turing Test, it also seems vulnerable to hard-ball inquisitorial tactics. There are probably quite a few questions you could ask which lie outside the ostensible scope of the debate, but which would correlate strongly with a user's true beliefs, or require faculties the respondent simply doesn't have in order to answer satisfactorily. I'm pretty sure if I asked a fake-atheist to name ten atheist-related figures that inspired them, they'd come up with a predictable, odd, or obviously Googled list. Equally, if I was posing as a Christian I'd struggle to name ten inspiring Bible passages that weren't either predictable, odd, or obviously pulled off Google.
You could just forbid tactics violating the spirit of the test, such as these ones.