Psychohistory, like psychoanalysis, is a science in which the researcher's feelings are as much or even more a part of his research equipment than his eyes or his hands. Weighing of complex motives can only be accomplished by identification with human actors, the usual suppression of all feeling preached and followed by most "science" simply cripples a psychohistorian as badly as it would cripple a biologist to be forbidden the use of a microscope. The emotional development of a psychohistorian is therefore as much a topic for discussion as his or her intellectual development.
"Foundations of Psychohistory". Book by Lloyd deMause, 1982.