The main purpose of this essay is to articulate a conceptual framework for early mental development. The content of the essay is based on a review of psychoanalytic literature and includes an attempt to integrate preverbal developmental data with the constructs of psychoanalytic theory. The view is taken that object constancy and the capacity to differentiate one's own and other persons' feelings, motives, and actions are necessary for the development of an independent, empathic person. Part One of the essay delineates the theoretical frame of reference. Topics discussed include (1) the family as an interacting system of relationships, (2) object relations as the internalization of interactions, and (3) general characteristics of the preverbal phases of development and related pathologies. Part Two explores the process of psychic differentiation. Both intrapsychic and interpersonal aspects of the differentiation process are described and a model of these different dimensions of the process is provided. A brief case illustration of family problems associated with undifferentiated psychic development is included at the end of the essay. (RH)