In this thesis Freud`s text named On transience (1916a [1915]) gets a new reading that allows a new discussion of the concept of consciousness and its relations to perception and to the development of the ego. In its transience the consciousness increases the value of the stimulus` ephemeral character, originating a concentration of enlightening. This path is imposed to it both by the unconscious wish and the perception. In narcissistic neuroses the stiffening of the transience of the consciousness takes on many forms, and the transference becomes a difficult work. The possibility to think therapy taking into account the transience of the consciousness in its relations to culture opens up new perspectives for a new understanding of psychoanalytic clinic.