A reconstruction of Freud's argument for the justification of the unconscious. Freud's justification for the hypothesis of the unconscious has been often reduced to its empirical components or to purely heuristic arguments. First, this paper aims to discuss Freud's strategy in introducing the concept of unconscious in his theory; next, to recapitulate the various arguments that justify it; and finally, to systematically reconstruct them, in order to put in evidence the semantic and conceptual aspects of the theoretical framework where the empirical proofs are inserted, as well as its convergence with similar strategies of contemporary programs of psychological research (cognitive science, for instance) which also operate with the hypothesis...