The word ‘PSYCO’ means mind and ‘LOGY’ means to study, it means that Psychology is the study of mental or brain process and also deals with human behavior. First William James defines psychology as the science of brain life in 1890. When psychology established as a science separate from biology and philosophy the debate will starts that how we describe and explain human behavior then different philosopher gives their thoughts, now a days known schools of thought. Some major schools of thought are define in this summary.