Therapeutic mediations are frequently used in mental health services. However, only a relatively small number of studies are designed to assess their effectiveness and analyze their effects from a psychoanalytical point of view. We propose in this paper a summary of the research in this area in order to develop a comprehensive theory of therapeutic mediation from a psychoanalytic perspective, which differs from art therapy by taking into account the effects of associativity and the different types of transference. Four hypotheses concerning the underlying processes of therapeutic mediation are proposed. First (1) there is a spontaneous tendency of psychic reality to “print” its mark in its environment in order to self-represents its own processes in an externalized manner. These processes concern essentially (2) non-symbolized psychic elements that will return during the therapeutic sessions and will be “projected” in the object of mediation. These non-symbolized elements will be expressed (3) depending on the sensory and current aspects of the mediation (4) and only if the mediation properties do echo the characteristics of psychic reality in a form of “resonance” between the psyche and the mediation. In conclusion, Current development of theories and evaluations in the field of therapeutic mediation expand our understanding of the nature of the effectiveness of these settings and also help the clinicians to improve the reflexivity of what is happening in the encounter with the object.