This paper is a psychoanalytic investigation into the experience of space in a schizoid borderline patient. Its aim is to show the correlation between mental space, corporeal space and the fantasy of the interior of the mother's body. This correlation can be viewed, in the light of Matte-Blanco's reconceptualization of the unconscious, as a symmetrical experience of being as a fused relation with the mother's body. The unfolding of this fantasy is followed in the psychoanalytic process of the patient. A hypothesis of the genesis of the difficulties in the development of asymmetrically discriminated spaces is offered. The psychoanalytic process allows the unfolding of symmetrical being in the transference. By way of this unfolding the patient's consciousness can start to discriminate his own space as different from the mother's body.