This thesis compares the psychological developmental models of Robert Kegan and Ken Wilber. Both theorists are neo-Piagetians in that they acknowledge the stage model of growth elaborated by Jean Piaget. However, in contrast to previous theorists, they have each independently created models based upon what they claim are the deep structures of the (already acknowledged) Piagetian stages of development, and not merely the expressions of those stages (e.g., cognition, morality, self-sense, etc.). Kegan and Wilber also acknowledge that the self contains multiple lines of development and organizes the unfolding of each developmental line according to its stage-specific identification. Wilber expands this idea of multiple lines of development, and introduces the probability that these lines are developing at different rates within any given individual. A proposed integration of the models of Kegan and Wilber is offered, centered around the line of object-relations. Although the importance of object-relations is widely recognized in terms of psychopathology (and Buddhist psychology), it's centrality as a line of development which organizes identification and subsequent stage unfoldment is what this thesis proposes.