Psychiatrist Carl Jung is credited with first introducing the term "complex" into the psychoanalytic lexicon. Prior to Jung's relatively brief but fruitful collaboration with him, Freud utilized an altogether different terminology to denote the now famous "Oedipus complex." Later, Alfred Adler, another of Freud's former followers, introduced the notion of an "inferiority complex."

According to Jung, a complex (e.g., a mother or father complex) is an unconscious constellation of cognitions, memories, images, impulsions, opinions, beliefs, associations and other content emanating from a core or nucleus of repressed or dissociated emotion, drive or instinct. Complexes can behave like relatively autonomous "splinter personalities," powerfully influencing consciousness, cognition, affect and behavior. As Jung once said, we all have complexes; the question is whether we have complexes or they have us.

Complexes contain archetypal images that lie latent in the unconscious until being somehow stimulated, at which time they can, in certain cases, take complete or partial possession of the personality. The idea and image of Messiah or God appear to be innate (archetypal) potentialities in the human psyche. When activation occurs, some confused individuals misidentify themselves with this archetypal image, resulting in a dangerous form of ego-inflation seen typically in schizophrenic patients, or those suffering from delusional disorder or severe manic episodes.