This article aims to present the contributions of Ludwig Wittgenstein to the foundation of psychological knowledge and practice. This will be done in two fundamental movements: first, we will reconstruct Wittgenstein's interlocutors (empirical psychology, phenomenology and Freudian psychoanalysis) and the questions that were presupposed in each of them (Cartesianism and imprecise use of language). Second, we will argue about the analytic method that Wittgenstein chose to deal with these questions. This means at least two things: (1) Wittgenstein assumes that the descriptive language (of facts in the world) is the standard for human interlocution, but that expressive language (of subjective occurrences) also has its place of importance, stil...