Choice without Beliefs

This paper provides an axiomatic foundation for decision making in complex settings in which the decision maker does not have complete structural knowledge of the environment. The agent knows the set of actions he can take, he formulates preferences directly on the actions, and chooses according to these preferences. On the basis of experience he modifies these preferences according to a systematic procedure. A group of natural structural restrictions and a group of independence axioms are imposed on this procedure. The main result is an axiomatic foundation for a set of simple adaptive learning procedures which include the replicator dynamic.