But it is a phenomenon in the sense that had traditionally defended the traditional philosophy, in fact, the Western philosophical tradition did see things consist, so to speak, two faces: the phenomenon and the noumenon. The phenomenon is what appears, while the noumenon is something that is hidden, unknowable that is the essence of the thing genuine and is beyond our knowledge mechanisms. Sartre, against this view, argues that the thing is pure phenomenon, namely that there is nothing to hide, but simply what appears is, and be or what it is, is what appears. The object thus understood is what Sartre called being in itself. Opposite him, consciousness is characterized as being for itself, the being for itself is nothing, in the sense that consciousness is always consciousness of something, ie is always directed to a being that is not itself, himself "I", sometimes identified with consciousness, comes to be something here that is not essentially different from the objects themselves, and is situated ontologically the same level as the phenomena of the external world. Consciousness is not understood as an entity "spiritual" or otherwise, but as an intentionality that is not in itself but has to relate to the world in which it is. Thus, in Being and Nothingness is announced ontological dualism between the nothingness of consciousness that tends perpetually to Overcoming the facticity and Being as presence of what is gross. Moreover, Sartre developed on the basis of an analytical grounds ethical marking in which is of particular relevance is the notion of freedom.