Rationality

Rationality is the quality or state of being reasonable, based on facts or reason. Rationality implies the conformity of one's beliefs with one's reasons to believe, or of one's actions with one's reasons for action. "Rationality" has different specialized meanings in economics, sociology, psychology, evolutionary biology and political science.

Determining optimality for rational behavior requires a quantifiable formulation of the problem, and making several key assumptions. When the goal or problem involves making a decision, rationality factors in how much information is available (e.g. complete or incomplete knowledge). Collectively, the formulation and background assumptions are the model within which rationality applies. Illustrating the relativity of rationality: if one accepts a model in which benefitting oneself is optimal, then rationality is equated with behavior that is self-interested to the point of being selfish; whereas if one accepts a model in which benefiting the group is optimal, then purely selfish behavior is deemed irrational. It is thus meaningless to assert rationality without also specifying the background model assumptions describing how the problem is framed and formulated.