The paper addresses the objectives of therapeutic work, emphasising processes of change which move an 'inadequate' state towards another, more 'adequate' one. Different types of change are considered, and the factors necessary for detecting them. Following the mathematical model, we distinguish between continuous and discontinuous change. In social processes also there are continuous changes, where a transition occurs cumulatively and slowly. In another type of change a drastic modification is produced, implying discontinuity and a sudden jump. On this point it is necessary to distinguish between removable discontinuities having little significance, and essential ones which have significant effects. 'Levels of change' imply categorial or structural differences. We consider different forms of obstacle which get in the way of the adequate management of change: non-perception of change on the part of the therapist, epistemological inertia and therapeutic zeal. We address the location of change in the psychoanalytic process in relation to the patient–analyst couple.