In decision theory and game theory, an alternative or strategy (2) that, in every contingency that might arise, yields a payoff at least as good as the payoff from any other available alternative or strategy and a strictly better payoff in at least one. A dominant strategy is strongly dominant if it yields a strictly better payoff than any other alternative or strategy in every possible contingency, otherwise it is weakly dominant. An alternative or strategy that is not dominated by any other is an admissible alternative/strategy, and in a decision problem in which a dominant strategy exists, another alternative or strategy that is not dominant is a dominated alternative/strategy or an inadmissible alternative/strategy. It is generally agreed that a rational decision maker or player will never deliberately choose a dominated alternative or strategy, but this principle appears counter-intuitive to some people in puzzles such as Newcomb's problem and the Prisoner's Dilemma game. Also called a dominating alternative/strategy. See also prospect theory, sure-thing principle.