In Lacan’s perspective, the cogito is unable to account for the separation between desire and language for the individual. The fundamental difference pertaining to the signifier (signifiant) makes it impossible for the enunciation (sum) to ever coincide with what is enunciated (sense). Therefore no final knowledge of self, being and reality (réel) is possible within the framework of the imaginary-symbolic life-world. This analysis, which is decisive for the therapeutic process, is then confronted with a radical-phenomenological critique that questions Lacan’s presuppositions about alterity from the perspective of a primal and transcendental life (Lebendigkeit), a confrontation that ought to bear fruit for the dialog between psychoanalysis and phenomenology.