In the absence of a generally accepted biopsychological theory, naturalistically inclined psychohistorians have only been able to establish speculative typologies of historical human behavior. Although the Freudian conflict theory has proven an attractive psychohistorical tool, it is inherently methodologically deficient, and its assimilation to salvationist ideologies has obscured its naturalistic aspects. Epidemiological data on the incidence and distribution of mental distress might prove invaluable in determining criteria for psychological survivability in a given culture, but little useful data of this kind have appeared. In analyzing revolutions, psychohistorians have failed to correlate conclusively such upheavals with specific shifts in the psychological makeup of the society in question.