Several scholars see Freud as parallel to Plato, writing that they hold nearly the same theory of dreams and have similar theories of the tripartite structure of the human soul or personality, even if the hierarchy between the parts of the soul is almost reversed. Ernest Gellner argues that Freud's theories are an inversion of Plato's. Whereas Plato saw a hierarchy inherent in the nature of reality, and relied upon it to validate norms, Freud was a naturalist who could not follow such an approach. Both men's theories drew a parallel between the structure of the human mind and that of society, but while Plato wanted to strengthen the super-ego, which corresponded to the aristocracy, Freud wanted to strengthen the ego, which corresponded to the middle class. Paul Vitz compares Freudian psychoanalysis to Thomism, noting St. Thomas's belief in the existence of an "unconscious consciousness" and his "frequent use of the word and concept 'libido' – sometimes in a more specific sense than Freud, but always in a manner in agreement with the Freudian use." Vitz suggests that Freud may have been unaware his theory of the unconscious was reminiscent of Aquinas.