J. Bouveresse's Philosophie, mythologie, pseudo-science: Wittgenstein lecteur de Freud was the first key to this study. It explains Wittgenstein's trenchantly critical stance towards Freudian theory - namely, that psychoanalysis has little to do with the realm of science, but much more with the realm of aesthetic research. The second key is the similarity between the Spinozist and Freudian approaches: an inflexible faith in hard determinism (as expressed by W. James in his article The Dilemma of Determism), a description of the human psyche (the interplay of affects and the Freudian topic), and a method for redirecting man's harmful determinism towards a happier one (the rational analysis of the causes that make us act and psychoanalysis).Three centuries apart, the same problem and the same foundations on which to answer it. Yet the Dutch philosopher's Ethics is described as metaphysical, while Freudian theory is described as scientific. This study offers an epistemological critique of Freudian theory from a Spinozist perspective.