Philip Pettit

If an agent is to be moved to action, then two requirements have to be fulfilled: first, the agent must possess beliefs about the way things actually are, about the actions possible given the way things are, and about the likely effects of those actions on how things are; and, second, the agent must have or form desires to change the way things are by resorting to this or that course of action. The beliefs tell the agent about how things are and about how they can be altered; the desires attract the agent to how things are not but can be made to be.

In order to vindicate rational-choice theory as a mode of explaining social patterns in general - social patterns beyond the narrow range of economic behaviour - we have to recognize the legitimacy of explaining the resilience of certain patterns of behaviour: that is, explaining, not necessarily why they emerged or have been sustained, but why they are robust and reliable. And once we allow the legitimacy of explaining resilience, then we can see how functionalist theory may also serve us well in social science; we lose the basis - the empty black box argumenton which the rational-choice critique of the theory has mostly been grounded