he study of the economic notion of preference can be undertaken through the perspective of non-monotonic logic. In this framework, qualitative utilities correspond to rational inference relations, and it is possible to apply, to the theory of utility, some representation theorems that hold for rational inference relations. This leads to a strong result, showing that the rational preferences of an agent are totally determined by a fundamental preexisting chain of alternatives. Such a chain provides a mental model for any rational agent, which can be used to guess the agent's undisclosed preferences and predict her future behavior.