By way of exploring the epistemology of Sigmund Freud's belief in the existence of the psychoanalytic unconscious and the specific methodology by which he constructed psychoanalysis,the paper reveals the metaphysical character in the idea of the unconscious in his psychoanalysis system.The authors argue that,because of its unconsciousness,the psychoanalytic unconscious as a realm of existence can by no means be intuited by either Sigmund Freud or anyone else.It is thus conceivable that Freud did accomplish a sound and complete articulation for the theoretical foundation of his psychoanalysis.The idea of the unconscious as a practical issue in his clinical analysis is not the same as that as a theoretical issue in his psychoanalytic system.Freud's detailed discussion of the former,therefore,cannot be received as argumentation for the latter.