The model of human occupation is an outgrowth of the occupational behavior tradition which emphasizes the original philosophical premises of the occupational therapy profession. The model employs general systems theory to explain the human system and its interaction with the environment. The model conceptualizes the human as an open system that consists of three subsystems: volition, habituation, and mind-brain-body performance. The subsystems are hierachically ordered from the highest to lowest and each subsystem has its own structure and function. The highest subsystem is referred to as volition which is responsible for freely and consciously choosing occupational behavior. The middle subsystem is habituation which organizes occupational behavior into patterns or routines. The lowest subsystem is mind-brain-body performance which makes possible the skilled achievement of occupations. The human is also understood as a dynamical system performing in an environment composed of objects, tasks, social groups, and culture. Although the language of the model may be unfamiliar at first the basic theoretical principles of the model share the common concept with those of the oriental philosophy. The model is recognized as a holistic and comprehensive model which is one of the first to develop a strong focus on occupation in the occupational therapy profession.