For a rational actor, the information he uses to shape his beliefs is a variable rather than a given. Before deciding how to act, he has to make a pr… - Jon Elster

The theory of rational action may therefore fail, because it is unable to produce unique prescriptions and predictions. It may also fail if the agents’ behavior does not conform to predictions, whether these are unique or not; that is, if the agents are irrational. There are multiple sources of irrationality, hot or cold.

Acting in conformity with reason, in the singular, and acting for good reasons, in the plural, are two different things insofar as reason is objective, whereas reasons are subjective. From an external point of view, we can evaluate a policy as being in conformity with reason or not. From an internal point of view, one can evaluate an action as being rational or not. From this difference it follows that only rationality can be used for explanatory ends. It is only insofar as the agent has made the demands of reason his own that the latter may give rise to, and possibly explain, specific behaviors. The assessment of the actor and that of the observer need not coincide.

In a general way, we can represent the present value of a future good as a function of the time separating the present from this future. In the classical conception, an exponential future discount is stipulated, which implies that the curves corresponding to two distinct future goods, one small and immediate, the other large and more remote, never intersect. According to more recent research, however, it seems that this discount typically takes a hyperbolic form.