Kegan's theory is discussed in terms of its relationships to Piaget and to psychoanalysis. Basing himself on Piaget's genetic epistemology, Kegan formulates a theory of human development extending throughout the life cycle. The theory postulates that individuals alternate between periods of concern with intimacy and concern with autonomy. For Kegan, what is conceived by the individual as part of the self (subject) at one stage becomes object at the next. While his work is considered to be an important contribution, Kegan is criticized on the grounds of conceptual vagueness and an overemphasis on developmental universals at the expense of the consideration of idiosyncratic aspects of individual development. Kegan is also criticized for appearing to believe that there is only one correct therapeutic approach.