Name: 絶対に解決できない問題 (A Problem You'll Never Solve)
Uploaded: 2021-01-14T08:16:23.000Z
Duration: 12 min
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

程度の副詞

Kevin here, with a really simple question.

Do you want this box of 1000 candies and a
mystery box which contains either nothing

Obviously you'll take both boxes because
you're getting the mystery box either way.

Might as well grab some guaranteed candy too,
right?

When it comes taking both boxes or just the
mystery box, almost everyone watching this

video will be absolutely sure that they know
the right answer.

This is barely a problem, let alone one you'll
never solve.

Half of you will be certain that the obvious
answer is to take both boxes, and the other

half of you will be just as sure the obvious
answer is to take only the mystery box.

And why is there suddenly a Grandayy genie
on my table?

It's literally clear -- you can see that
the contents are 1000 candies.

The contents of Box B are determined in advance
by our omniscient, all-knowing Grandayy genie,

who predicts what you'll choose with near-perfect
accuracy.

If he predicts you'll choose both boxes,
he's put nothing in Box B.

If he predicts that you'll only choose mystery
Box B, he's placed… a million candies.

You can't see inside Box B, you can't
touch it, and you don't know what the genie

has predicted before you actually choose.

Theoretical physicist William Newcomb devised
this problem in 1960.

And a decade later, philosopher Robert Nozick
detailed the deep philosophical fracture that

makes the two equally-obvious choices both
right and both wrong.

If you decide to take both boxes, the genie
will likely have predicted that and put nothing

in mystery Box B -- maybe genies don't like
greedy players or something.

So if you choose both Box A and box B, you'll
wind up with only a few handfuls of candy.

If you decide to take only mystery Box B,
the genie will almost certainly have predicted

that, too, and put a million candies inside…
maybe as a reward for your courageous choice.

Either way, it's now obviously better for
you to take mystery Box B because a million

That's one way to look at this problem,
and in a 2016 poll from The Guardian, 53.5%

of over 30,000 survey respondents chose to
take only mystery Box B. Here's what the

The genie has already either put a million
candies in the mystery box… or not.

He could've setup the boxes a day, a week,
a month ago!

The candy isn't going to suddenly appear
or disappear based on your decision.

If he's filled Box B with candy and you
take both boxes, you'll get a million plus

1000 more from Box A, which you can eat right
away to celebrate your amazingly clever rationale.

If he didn't fill Box B… he just didn't.

You take both boxes and win your small prize
and this way you don't walk away empty-handed.

Worst case scenario, the mystery box is empty
but you still get 1000 pieces of candy which

So should you take both boxes or just Box
B?

Why exactly has Newcomb's Paradox confounded
minds for decades?

Because it's pitting two equally valid methods
of reasoning against each other: Expected

Let's recap the two options with a little
math… so we can get serious.

You may not have a sweet tooth, so let's
switch prizes from candy to money: Box A now

contains $1,000, and Box B either has $1 million
dollars or no dollars.

First, we can see our possible outcomes with
a simple payoff matrix.

Basically, we'll just write out the four
scenarios.

If the genie predicts you'll take Box B
and you choose Box B, you'll get $1,000,000.

If he predicts you'll take Box B but you
choose both boxes, you'll win $1,001,000

-- the million in Box B and the $1,000 in
Box A.

If he predicts you're greedy and will take
both boxes but you choose just Box B, then

And if the Genie's prediction is both boxes,
and you choose both boxes, your prize is just

To put it another way, these are the outcomes
when his prediction is right and these are

the outcomes when his prediction is wrong.

We mapped out the potential outcomes, now
what?

How do we figure out which choice is right?

Well, we can actually calculate how valuable
a choice is to you -- that's Expected Utility.

You simply take the result of a choice and
multiply it by the probability of the outcome.

That'll give you a numerical value to help
inform your decision.

So, let's say the genie has a 90% chance
of predicting right.

We'd calculate the expected utility of choosing
both boxes like this:

A 90% chance he's right means there's
a 10% chance that he's wrong.

So if we choose both boxes, there's a 10%
chance we win two money-filled boxes and a

90% chance that we're left with just the
$1,000.

We multiply the .1 probability that he's
wrong by the payoff of $1,001,000 from both

boxes and add that to the 90% chance he's
right, which means Box B would be empty -- so

that's .9 multiplied by just the $1,000
Box A payoff.

If we assume that the genie is right 9 times
out of 10, each time we chose both boxes,

Now let's find the Expected Utility of choosing
only Box B so that we can compare the two

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絶対に解決できない問題 (A Problem You'll Never Solve)

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perception

obvious

scenario