Direct-revelation_mechanism
The revelation principle is a fundamental result in mechanism design, social choice theory, and game theory which shows it is always possible to design a strategy-resistant implementation of a social decision-making mechanism (such as an electoral system or market).[1] It can be seen as a kind of mirror image to Gibbard's theorem. The revelation principle says that if a social choice function can be implemented using some non-truthful mechanism (one where players have an incentive to be dishonest), the same function can be implemented by a truthful mechanism which has the same equilibrium outcome (payoffs).[2]: 224–225
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The revelation principle shows that, while it is impossible to design a system that will always be invulnerable to any strategy if we do not know which strategy the players would use, it is possible to design a system that is strategy-resistant for any given solution concept (when the strategies of players are known).[3][4]
The idea behind the revelation principle is that, if we know which strategy the players in a game will use, we can simply ask all the players to submit their true payoffs or utility functions; then, we take those preferences and calculate each voter's optimal strategy before executing it for them. This procedure means that an honest report of preferences is now the best-possible strategy, because it guarantees the mechanism will play the optimal strategy for the player.