  Indifference of a player with respect to two distinct outcomes of a game
cannot be handled by small perturbations, because the actual choice may have
significant impact on other players, and cause them to act in a way that has
significant impact of the indifferent player. It is argued that ties among
rational choices can be resolved by refinements of the concept of rationality
based on the utilities of other players. One such refinement is the concept of
Tit-for-Tat.
