Means the development of differences, the separation of parts from a whole. In this work I employ the concept chiefly in respect to psychological functions. So long as one function is still so merged with one or more of the other functions—as for example thinking with feeling, or feeling with sensation, etc.—as to be quite unable to appear alone, it is in an archaic (q.v.) state, and therefore undifferentiated, i.c. it is not separated out as a special part from the whole having its own independent existence. An undifferentiated thinking is incapable of thinking apart from other functions, i.e. it is constantly mixed up with sensations, feelings, or intuitions; such thinking may, for instance, become blended with sensations and phantasies, as exemplified in the sexualization (Freud) of feeling and thinking in neurosis. The undifferentiated function is also commonly characterized by the qualities of ambivalency and ambitendency , i.e. every positive brings with it an equally strong negative, whereby characteristic inhibitions spring up in the application of the undifferentiated function. Such a function suffers also from a fusing together of its individual parts; thus an undifferentiated faculty of sensation, for instance, is impaired through an amalgamation of the separate spheres of sensation ("audition coloriée"), and undifferentiated feeling through confounding hatred with love. Just so far as a function is wholly or mainly unconscious is it also undifferentiated, i.e. it is not only fused together in its parts but also merged with other functions.
Differentiation consists in the separation of the selected function from other functions, and in the separation of its individual parts from each other. Without differentiation direction is impossible, since the direction of a function is dependent upon the isolation and exclusion of the irrelevant. Through fusion with what is irrelevant, direction becomes impossible'; only a differentiated function proves itself capable of direction.