Freud's desire to subsume his psychology under the umbrella of natural science, a desire stemming from his allegiance to Mach's doctrine of the unity of science, ran contrary to the dualistic epistemological zeitgeist. This epistemological dualism was nested within an ontological dualism that was virtually taken for granted by the educated German-speaking public; from this vantage point, Freud's monism was regarded as deeply counter-intuitive.