This paper explains how A. Bogdanov changed from a left Bolshevik impatient for armed insurrection into a moderate proponent of revolution through cultural transformation by placing him in the context of a debate over epistemology among Russian Social Democrats in the early twentieth century. By relying on neo-Kantian epistemology to justify socialist revolution, N. Berdyaev actually began to turn away from Marxism. Lenin espoused a naive realism that was consistent with scientific socialism, but which did not satisfy Bogdanov. Empiriomonism, Bogdanov's neo-Positivist epistemology, led him away from violent revolution and toward a proletarian cultural revolution.