Abstract
Psychohistory is a limited historical tool, best used in inquiries about irrational behavior and beliefs. Irrational behavior is either an unsuitable means for accomplishing the agent's self-proclaimed purposes or an inappropriate response in terms of social norms. When the agent's behavior displays internal inconsistencies, the historian must look beyond the agent's own reasons. But before looking for unconscious motives, the historian must reconstruct the objective situation from the historical standpoint of the agent to see if the action is intelligible in its context. Irrational beliefs are those which are impervious to disconfirming factual evidence. It is the thought processes behind beliefs which determine their rationality; irrational beliefs only make sense in terms of the social and emotional needs they fulfill.