When a reliable predictor has already acted on a prediction of your choice, taking one box and taking both are each defensible, and decision theory divides on which is right.
Newcomb devised it and Nozick published it in 1969. A predictor who has been right almost every time has put either a fortune or nothing into the opaque box, according to whether it predicted you would take that box alone. Causal reasoning says the contents are already fixed, so take both. Evidential reasoning says that one-boxers end up rich, so take one. Nozick reported that people divide sharply and each side thinks the other is simply failing to see it.
In practice
- An employer who reads candidates well has priced the offer before the negotiation starts.
- A friend who knew you would cancel has already made other plans, which is what you discover when you do not cancel.
- Standing
- A live problem in decision theory rather than a claim about behaviour, and the standard test case between causal and evidential decision theory.
- Further reading
- Wikipedia
- Subject
- Decision-making & Reasoning
- Essay
- Paradoxes that broke theories, and sayings that outlived them