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  • I'd like to introduce you to a particularly powerful paradigm for thinking called Bayes'

  • Rule. Back in the Second World War the then governor of California, Earl Warren, believed

  • that Japanese Americans constituted a grave threat to our national security. And as he

  • was testifying as much to Congress, someone brought up the fact that, you know, we haven't

  • seen any signs of subterfuge from the Japanese American community. And Warren responded that,

  • "Ah, this makes me even more suspicious. This is an even more ominous sign because that

  • indicates that they're probably planning some major secret timed to attack á la Pearl Harbor.

  • And this convinces me even more that the Japanese Americans are a threat."

  • So this pattern of reasoning is what sustains most conspiracy theories. You see signs of

  • a cover up -- well, that just proves that I was right all along about the cover up.

  • You don't see signs of a cover up, well that just proves that the cover up runs even deeper

  • than we previously suspected.

  • Bayes' Rule is provably the best way to think about evidence. In other words, Bayes' Rule

  • is a formalization of how to change your mind when you learn new information about the world

  • or have new experiences. And I don't think that the math behind -- the math of Bayes'

  • Rule is crucial to getting benefit out of it in your own reasoning or decision making.

  • In fact, there are plenty of people who use Bayes' Rule on a daily basis in their jobs

  • -- statisticians and scientists for example. But then when they leave the lab and go home,

  • they think like non-Bayesians just like the rest of us.

  • So what's really important is internalizing the intuitions behind Bayes' Rule and some

  • of the general reasoning principles that fall out of the math. And being able to use those

  • principles in your own reasoning.

  • After you've been steeped in Bayes' Rule for a little while, it starts to produce some

  • fundamental changes to your thinking. For example, you become much more aware that your

  • beliefs are grayscale, they're not black and white. That you have levels of confidence

  • in your beliefs about how the world works that are less than one hundred percent but

  • greater than zero percent. And even more importantly, as you go through the world and encounter

  • new ideas and new evidence, that level of confidence fluctuates as you encounter evidence

  • for and against your beliefs.

  • Also I think that many people, certainly including myself, have this default way of approaching

  • the world in which we have our preexisting beliefs and we go through the world and we

  • pretty much stick to our beliefs unless we encounter evidence that's so overwhelmingly

  • inconsistent with our beliefs about the world that it forces us to change our minds and,

  • you know, adopt a new theory of how the world works. And sometimes even then we don't do

  • it.

  • So the implicit question that I'm asking myself that people ask themselves as they go through

  • the world is when I see new evidence, can this be explained with my theory. And if yes,

  • then we stop there. But, after you've got some familiarity with Bayes' Rule what you

  • start doing is instead of stopping after asking yourself can this evidence be explained with

  • my own pet theory, you also ask well, would it be explained better with some other theory

  • or maybe just as well with some other theory. Is this actually evidence for my theory.

I'd like to introduce you to a particularly powerful paradigm for thinking called Bayes'


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B1 中級

ジュリア・ガレフベイズのルールで合理的に考える (Julia Galef: Think Rationally via Bayes' Rule)

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    Book に公開 2021 年 01 月 14 日