decisions · paradox
Newcomb's paradox
One box or both, and the predictor has already packed them.
The yellow box was packed before you choose. A predictor that is almost always right put $1 million in it if it thought you would leave the clear box, and left it empty if it thought you would take both. The clear box has $1,000 either way. The packing is finished. Do you take only the yellow box, or both?
Packed before you choose
Clear box. You can see it.
Yellow box. You cannot see inside.
Only the yellow box: $1 million
Both boxes: $1,000, and the yellow box is empty
The yellow box is the opaque one. Opaque means you cannot see inside, and the predictor will not repack it after you choose.
If the predictor expected you to take only the yellow box, that box holds $1 million. If it expected you to take both, the yellow box is empty and you still get the $1,000 you can see.
One reason says the boxes are already packed, so taking both pays $1,000 more than taking one, whatever is inside the yellow box.
The other reason says the predictor is almost always right, so the people who take only the yellow box are the ones who find $1 million.
Those two reasons disagree. That is Newcomb's paradox.
Kavka's toxin puzzle pays you tonight for intending to drink a mild toxin tomorrow, and tomorrow the money is already settled.