Newcomb's Problem and Two Principles of Choice |
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Nozick (Robert) |

Source: N. Rescher et al. (eds.), Essays ín Honor of Carl G. Hempel. 1969. |

Paper - Abstract |

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__Author’s Introduction__

- Suppose a being in whose power to predict your choices you have enormous confidence. (One might tell a science-fiction story about a being from another planet, with an advanced technology and science, who you know to be friendly, etc.) You know that this being has often correctly predicted your choices in the past (and has never, so far as you know, made an incorrect prediction about your choices), and furthermore you know that this being has often correctly predicted the choices of other people, many of whom are similar to you, in the particular situation to be described below. One might tell a longer story, but all this leads you to believe that almost certainly this being's prediction about your choice in the situation to be discussed will be correct.
- There are two boxes, (Bl) and (B2). (B1) contains $1000. (B2) contains either $1000000 ($M), or nothing. What the content of (B2) depends upon will be described in a moment.
- You have a choice between two actions:
- taking what is in both boxes
- taking only what is in the second box.

- Furthermore, and you know this, the being knows that you know this, and so on:
- If the being predicts you will take what is in both boxes, he does not put the $M in the second box.
- If the being predicts you will take only what is in the second box, he does put the $M in the second box.

- The situation is as follows. First the being makes its prediction. Then it puts the $M in the second box, or does not, depending upon what it has predicted. Then you make your choice. What do you do?
- There are two plausible looking and highly intuitive arguments which require different decisions. The problem is to explain why one of them is not legitimately applied to this choice situation. You might reason as follows:
*First Argument*: If I þke what is in both boxes, the being, almost certainly, will have predicted this and will not have put the $M in the second box, and so I will, almost certainly, get only $ 1000. If I take only what is in the second box, the being, almost certainly, will have predicted this and will have put the $M in the second box, and so I will, almost certainly, get $M. Thus, if I take what is in both boxes, I, almost certainly, will get $1000. If I take only what is in the second box; I, almost certainly, will get $M. Therefore I should take only what is in the second box.*Second Argument*: The being has already made his prediction, and has already either put the $M in the second box, or has not. The $M is either already sitting in the second box, or it is not, and which situation obtains is already fixed and determined. If the being has already put the $M in the second box, and I take what is in both boxes I get $M + $1000, whereas if I take only what is in the second box, I get only $M. If the being has not put the $M in the second box, and I take what is in both boxes I get $1000, whereas if I take only what is in the second box, I get no money. Therefore, whether the money is there or not, and which it is already fixed and determined, I get $ 1000 more by taking what is in both boxes rather than taking only what is in the second box. So I should take what is in both boxes.

- Let me say a bit more to emphasize the pull of each of these arguments: …

For the full text, see Nozick - Newcomb's Problem and Two Principles of Choice.

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