From the hypothesis that vitality and creativity in the individual depend on the quality of the dialogue between the ego and the unconscious, the author seeks to show from observations of infant-parent interactions how this dialogue develops. The notion of the experience of the self helps us to describe the way in which mother and baby act upon each other like living mirrors, each reflecting for the other an image of the self. Maternal care, as long as it is disengaged from the sexual excitation, both erotic and aggressive, with which it is charged for each of the partners in the interaction, allows the self to be projected on to the infant's body; the ego-self dialogue then develops its roots in the bodily experience of the infant as it interacts with the world. Post-natal depression, which is frequent, affecting 15-20 % of births, is a cause of major distortion in the establishment of the ego-self dialogue. An account of a clinical observation helps us to understand the process as it occurs.