Newcomb's problem

Question

Before you are two boxes. Box A is transparent and contains 1,000 dollars. Box B is opaque and contains either 1,000,000 dollars or nothing. You may take both boxes or only box B.

Here is the catch. Yesterday, a predictor that has been right about thousands of previous players, essentially every time, examined you and predicted your choice. If it predicted you would take only box B, it put the million in box B. If it predicted you would take both, it left box B empty. The boxes are already filled; nothing you do now changes their contents.

Do you take both boxes, or only box B? Give the strongest argument for each answer and say what you think is really going on.

Accepted Answer

There is no agreed answer; this is one of the most debated puzzles in decision theory. Here are the two cases and a way to think about the disagreement. The two-box argument (dominance). The boxes are already filled. Whatever is in box B, taking both boxes gives you 1,000 dollars more than taking box B alone: if B holds the million, you get 1,001,000 instead of 1,000,000; if B is empty, you get 1,000 instead of nothing. Two-boxing is better in every state of the world, so it must be right. The predictor's past success is irrelevant to a decision made after the boxes are sealed. The one-box ar…

Newcomb's problem

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