Personality theories tend toward the philosophical as they are founded more on uncontrolled observation than on scientific method. Major approaches to personality theory are:

1. Psychoanalytic
2. Trait
3. Humanistic
4. Cognitive

Standing apart from psychoanalysis, the field of personality psychology was developed in the 1930's by Harvard theorists Murray and Allport.

Murray says that two kinds of needs, basic (primary needs) and learned (secondary needs), shape personality. The "press" of external events aids or blocks fulfillment of these needs. Needs and press combine to create the "thema".