This paper explores the « basic endo-psychical situation » described by Fairburn. This situation is that of a split « ego » ; in other words, a schizoid position that Fairburn considered to be central, and is the basis for his theory of mental structure. The « basic endo-psychical situation » is made up of three structures of the « ego » which, while roughly corresponding to Freud’s tripartite division, are conceived as « ego » structures that are intrinsically dynamic in relation to each other. It is the anti-libidinal ego structure, or « internal saboteur » that occupies the central position in this text.