This work reflects a theoretical study about pain as a subject, emphasizing its conceptual aspect, not only the historical-philosophical point of view, but also the medical, psychopathological and especially psychoanalytical point of view. As pain intersects various discussions, without an epistemological defined field, it is proposed as a hypothesis, to define exactly in this transdiciplinary convergency: pain as a unique concept in the psychophysical interface that has as Modern dualist way of counterpart thinking. The psychoanalysis highly contributes to interrupting this parallelism. Going through the Freudian theory from the manuscripts to the studies of hysterical suffering, current neurosis, theory of pulsions, that gradually create significant variables which tend to maintain the pain exactly in the border of the real and symbolical body, of the representable and irrepresentable; between the life and death pulsions and between pleasure and displeasure. This hyphotesis is illustrated with fragments of cases related by physicians. It is questioned part of the psychosomatic psychoanalytical thought that maintains an asymmetric relationship between body and psyche by complex theorizing, which privilege the pain in psycho determinism, counteracting what is done by the medicine, paradoxically, with the anatomic body. The pain will not be in the duality of the subject, but as a metaphor of the unity.