Tangential, but Quirrel’s line here has always seemed mistaken to me:
There is nothing you can do to convince me because I would know that was exactly what you were trying to do.
That’s not how evidence works. If I’m trying to convince you that seven is prime, I can show you the proof, and that should convince you even if you know that’s what I’m trying to do. If I’m trying to convince you that I can do a backflip, I can do a backflip, and that should convince you even if you know I’m trying to convince you. (I can’t do a backflip.)
It’s true that if you know I’m trying to convince you, some actions I can take will provide different weights of evidence to you, than if you didn’t know that. Simply saying I can do a backflip will be less convincing if you know I’m trying to convince you that I can do a backflip, versus if you think my goal is “say a true fact about myself”. And in context, there may indeed be nothing Harry can do to convince Quirrel that he’s not an aspiring dark lord. But the general point seems untrue.
Yeah I totally agree and have always thought that about the line as well. My steelman of it is that he means “nothing” in a more handwavy way, but it’s still important to point out what you’re saying I think.
Oh, Quirrell is referring to what game theorists call Cheap Talk. If the thing I’m trying to convince you of is strictly in my own brain—like whether I intend to cooperate or defect in an upcoming Prisoner’s Dilemma—then any promises I make are, well, cheap talk. This is related to costly signals and strategic commitment, etc etc.
Anyway, I think that’s the missing piece there. “Nothing you can do to convince me [about your own intentions] [using only words]”.
Tangential, but Quirrel’s line here has always seemed mistaken to me:
That’s not how evidence works. If I’m trying to convince you that seven is prime, I can show you the proof, and that should convince you even if you know that’s what I’m trying to do. If I’m trying to convince you that I can do a backflip, I can do a backflip, and that should convince you even if you know I’m trying to convince you. (I can’t do a backflip.)
It’s true that if you know I’m trying to convince you, some actions I can take will provide different weights of evidence to you, than if you didn’t know that. Simply saying I can do a backflip will be less convincing if you know I’m trying to convince you that I can do a backflip, versus if you think my goal is “say a true fact about myself”. And in context, there may indeed be nothing Harry can do to convince Quirrel that he’s not an aspiring dark lord. But the general point seems untrue.
Yeah I totally agree and have always thought that about the line as well. My steelman of it is that he means “nothing” in a more handwavy way, but it’s still important to point out what you’re saying I think.
Oh, Quirrell is referring to what game theorists call Cheap Talk. If the thing I’m trying to convince you of is strictly in my own brain—like whether I intend to cooperate or defect in an upcoming Prisoner’s Dilemma—then any promises I make are, well, cheap talk. This is related to costly signals and strategic commitment, etc etc.
Anyway, I think that’s the missing piece there. “Nothing you can do to convince me [about your own intentions] [using only words]”.