Newcomb's Problem is a thought experiment in decision theory exploring problems posed by having other agents in the environment who can predict your actions.

The Problem

From Newcomb's Problem and Regret of Rationality:

A superintelligence from another galaxy, whom we shall call Omega, comes to Earth and sets about playing a strange little game. In this game, Omega selects a human being, sets down two boxes in front of them, and flies away.

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