The ascetic experience and practice of mental prayer of Elder Joseph the Hesychast in this work are interpreted from the perspective of contemporary psychoanalytic theory. It starts form the phenomenological theory of perception and relation between dualism (invisible-visible, inside-outside, mind-body) and totality. In his letters, Elder Joseph the Hesychast reported on the internal contents that he had experienced in relation to the body; therefore, interpretations of these processes according to the theory and case studies of psychoanalysts Sigmund Freud and Melanie Klein have been presented. The understanding of a prayer through the terminology of Lacan’s Mirror stage has also been submitted. Owing to the rhythm of a mental prayer by which the control over the body is achieved, as a constant that maintains a clear distinction between the phantasmatic and the real, Elder Joseph the Hesychast’s prayerful speech is exceptionally stable in the big A. This furthermore allows overcoming the phantasmatic relation а-а’ and achieves the possibility of establishing the communication between A and S. Only in this way is it possible to touch the starting position S – the only one in which the subject is in its being.