The main task of this work is a presentation the topic of the unconscious, which is strictly associated with psychological and psychotherapeutic practice. The article concerns the functioning of the notion of the unconscious in the realm of different parts of knowledge. It analyses different meanings associated with this notion and the functions it performs in various conceptions. Furthermore, the text traces back the emergence and development of thought on the unconscious in philosophy, psychology and history of ideas. The term unconscious is used here in the most general sense, subsuming other forms of negating consciousness, such as unconsciousness and subconsciousness. The author strives to present the growth of reflection about the unconscious from the point of view of changing paradigms. By referring to H.Schnadelbach's schema, he derives the discourse on the unconscious from the criticism of problem solutions proposed by the mentalist paradigm in philosophy, as represented by Descartes and Kant. Seen from this perspective, the notion of the unconscious is intended to overcome the ontological dualism between thinking and extended substance and the dualism between phenomena and things in themselves. This theme emerges in the metaphysical discourse on the unconscious. On the other hand, anthropological discourse on the unconscious springs from the difficulty of perceiving human beings as composed of body and soul, ontologically distinct from each other. Seen from this perspective, discourse on the unconscious serves to overcome the basic psychological mind-body problem.