 For final moves, standard decision theory suggests that a choice is best for the active player if no other move leads to a better outcome. When extending the analysis to earlier positions of the game, things depend crucially on players’ expectations about their opponents’ future behavior. Several possible policies exist, depending on the types of player involved. A widespread assumption in epistemic game theory is common belief in rationality, i.e., that all players involved are rational, believe their opponents to be rational, believe their opponents to believe that opponents are rational, and so on. In line with this assumption, the following algorithm extends the \(\best_i\) relation recursively to non-terminal nodes: