Abstract Daniel Dennett advocates the use of the intentional stance in adaptationist biology and in cognitive ethology. He sees intentional system theory as closely related to decision theory and game theory. In biological decision and game theory models, nature ?chooses? the strategy by which the animal chooses a course of action. The design of the animal imposes constraints on the model. For Dennett, by contrast, the description of nature's rationale imposes constraints on the design of the animal. Dennett's oversimplified conception (...) of nature's rationale undermines the usefulness of the intentional stance as a tool in cognitive ethology. Intentional system theory can be made more useful in investigating animal cognition by modifying its application to questions of biological function. (shrink)