The object of this paper is to provide a metapsychological definition of alexithymia as described in 1967 in terms of operational thinking and negative hallucination. This is a familiar and established concept in the fields of psychopathology, psychology, and of clinical and psychosomatic medicine. From a psychoanalytic and psychosomatic point of view, the term is conceptually close to P. Marty's "operative thinking", as described in 1963, even though we know they do not belong to the same epistemological field: on one hand Neuroscience, Psychiatry and the objectalization of the symptom at different levels, and on the other, as regards mechanical functioning, a psychoanalytic clinical approach within the dynamics of the relationship between transference and counter-transference. The present authors consider that Freudian metapsychology, as now complexified by Andrè Green, allows for a metapsychological approach to alexithymia insofar as it relates to Marty's operative thinking. Thus does Green's conceptualization of the mother's negative hallucination, of negative introjection, of a psychically 'dead (and insecure) mother', now provide us with the opportunity to describe, in metapsychological terms, the genesis of this particular mode of psychical functioning. Given the mother's negative hallucination produces a host structure as a background to negativity that will fit future object representations, we will assume that in the case of … future operational or alexithymic …?, this negative hallucination will pathologically and defensively involve the endo-psychic perception of affect.