Concentration on the elaboration of a complicated nomenclature, which reached its climax in the work of Kraepelin, marked the dominance of fundamentalism in psychiatry, its characteristic being the descriptive and diagnostic attitude of the observers. Modernism in psychiatry was ushered in by World War I, with increased emphasis on therapy that followed recognition of the truth of the data concerning the unconscious. Psychiatry changed from static to dynamic concepts and was furthered by research on the childhood years and on the technique of analysis, with its application to the understanding of criminal behavior.