Rationality and the structure of human memory

A tacit and highly idealized model of the agent's memory is presupposed in philosophy. The main features of a more psychologically realistic duplex (orn-plex) model are sketched here. It is argued that an adequate understanding of the rationality of an agent's actions is not possible without a satisfactory theory of the agent's memory and of the trade-offs involved in management of the memory, particularly involving “compartmentalization” of the belief set. The discussion identifies some basic constraints on the organization of knowledge representations in general.