The author argues that if one intends to reconstruct in a theoretically adequate manner the empirically observable interaction of somatic and psychological data on the so-called “psychosomatic diseases in the strict sense”, there is a need for meta-theoretical mediation of area-specific theories. Furthermore, the author presents a concept of symptom formation of these diseases on the basis of Felix Deutsch’s understanding of conversion in which the somatic symptom is conceptualised in accordance with basic psychoanalytic insights and with the rational content of scientific medical knowledge.