THE PHYLOGENY OF RATIONALITY

A rational agent has beliefs reflecting the state of its environment, and likes or dislikes its situation. When it finds the world not entir ely to its liking, it tries to change that. We can, accordingly, evalu ate a system of cognition in terms of its probable success in bringing about situations that are to the agent's liking. In doing this we are viewing practical reasoning from ''the design stance.'' It is argued that a considerable amount of the structure of rationality can be elic ited as providing the only apparant solutions to various logical and f easibility problems that arise in the course of trying to design a rat ional agent that satisfies this design specification.