My dissertation examines the relationship between the scientific study of human thought and behavior and political projects of individual and social change in Russia and the Soviet Union, from the early 1900s to the Great Purges of the late 1930s. I focus specifically on a cluster of interrelated disciplines known in Russia as the psychoneurological sciences, which together promised to provide a unified science of the human subject. Such knowledge was seen by many throughout the period as a key to producing a better society and a more healthy, conscious, and virtuous person. Placing Bolshevik ambitions for the creation of "New Man" within this broader chronological and intellectual frame, I hypothesize that the psychoneurological sciences served to define both the conditions of possibility and the very limits of human transformation, with profound implications for the fate of the revolutionary project throughout. To test this hypothesis, I will examine the theoretical and practical developments of these experimental sciences of the human subject from the founding of V. M. Bekhterev's Psychoneurological Institute in St. Petersburg in 1904, through their proliferation in the early Soviet period and application to domains of labor, propaganda, child development and national minority integration, to their eventual liquidation by decree in 1936. By reconsidering the relation of science and ideology in early twentieth century Russian history, my research will contribute to significant debates within the field, including questions of expertise and the state, of continuity across the revolutionary divide, and of connections and commonalities between Soviet Union and western Europe. In this way, my project will offer a reappraisal of what is often dubbed the Great Experiment, not simply as an experiment in the building of socialism, but as an experiment in the application of scientific knowledge of the human subject to the management and ordering of human affairs.