After dealing with the question of why a consensual model of personality is required, two major assumptions are presented concerning the suggested model: that personality is a system and that it consists of interrelated levels. The four major levels of personality are described: the biological (genetic and physiological), the behavioral, the emotional and the cognitive, emphasizing the characteristic components and processes in each. Major functions resulting from interactions between these levels are presented, including creativity and traits. Personality is defined as a dynamic, developing system, capable of change. Self is considered as an experientially-based construct distinct from personality. Theoretical and methodological implications are presented laying the groundwork for the specific discipline of personality underlying the major branches of psychological science.