Daily Archives: June 20, 2010

Pick a Number

Economist Rob Hanson quoted Tyler Cowen from George Mason University:

We often like to ask lunch visitors what is their most absurd view (in the eyes of others). Alas I have so many choices. On BloggingHeads, Tyler Cowen answers this for Will Wilkinson:

Tyler: My most absurd belief, perhaps, is the extent to which I think people should be truly uncertain about almost all of their beliefs. And it doesn’t sound absurd when you say it but I don’t on the other hand know anyone who agrees with it. … Take whatever your political beliefs happen to be. Obviously the view you hold you think is most likely to be true, but I think you should give that something like 60-40, whereas in reality most people will give it 95 to 5 or 99 to 1 in terms of probability that it is correct. Or if you ask people what is the chance this view of yours is wrong, very few people are willing to assign it any number at all. Or if you ask people who believe in God or are atheists, what’s the chance you’re wrong – I’ve asked atheists what’s the chance you’re wrong and they’ll say something like a trillion to one, and that to me is absurd, that even if you think all of the strongest arguments for atheism are correct, your estimate that atheism is in fact the correct point of view shouldn’t be that high, maybe you know 90-10 or 95 to 5, at most. So that maybe is my most absurd view. Most things are much more up for grabs than we like to say they are.

Will: I agree with you that things are more up for grabs than people think they are, but I have real problems with the idea that it’s either possible or desirable that people assign probabilities to all of their beliefs. I think it’s a weird violation of the actual computational constraints of the human mind, that we just don’t.

Tyler: Here, you are more of a philosopher than I am, and I’m more a Bayesian. I’m sure it’s possible. Now I’m not saying it’s desirable, I’m just saying I want people to do it in a lot of instances, maybe just for my aesthetic pleasure. I want to pin people down and get a sense for how sure they are, and interpret these probabilities as betting odds, if you want. Let’s say there’s a lot of dying starving children in India or sub-Saharan Africa, and you are offered to bet, and you know that the money won on these bets will go to feed these children and save their lives, and you have to name what odds you are going to bet at. And you can name a number. You want to name the best number you can because you want to save the lives of these children, so I’m not going to allow any evasion here. I don’t see why there is not always some pick of a number that’s better than a lot of other picks. You are not going to get it right so computationally of course it’s hopeless. But look, you’ve got to give it your best guess. (emphasis added)

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