Jung was Freud's main collaborator and most probable successor as leader of the psychoanalytic movement, but his own researches led him away from Freud's emphasis on the psychosexual origins of neurosis, founding his own analytic psychology in response to Freud's psychoanalysis. This differed from the Freudian model in downgrading the importance of sexuality a childhood conflicts in the treatment of neuroses, and concentrating more on a patient's current conflicts. Jung's doctoral dissertation was entitled "On the Psychology and Pathology of So-Called occult Phenomena" and was presented at Basel University in 1902. This stuffy sowed the seeds of ideas that became pivotal in the practice of Jung's system of analytical psychology, namely that the unconscious contains "complexes" or part-personalities that can manifest in dreams and visions, and that personality development and integration (individuation) occurs at the unconscious level. A "complex" is a pattern of suppressed thoughts and feelings that cluster-constellate-around a theme provided by some archetype (archetype will be explained further on). Jung describes a "complex" as a "node" in the unconscious; it may be imagined as a knot of unconscious feelings and beliefs, detectable indirectly, through behavior that is puzzling or hard to account for. Jung found evidence for complexes in the "word association test"; here a researcher read a list of words to each subject, who was asked to say, a quickly as possible, the first thing that came to mind in response to each word. Researches timed subject's responses and noted any unusual reactions- hesitations, slips of the tongue, and signs of emotion. In Jung's theory, complexes may be related to traumatic experiences or not. There are many kinds of complex, but at the core of any complex is a universal pattern of experience, or archetype.
Few contemporary psychologists shared his view that psychological development, the growth towards the realization on an individual's true potential continued throughout the whole of life rather than being limited to childhood. Such self-realization could occur, Jung argued, by treating the unconscious as a living, daemonic presence: by confronting and examining what the unconscious has to say, a person can come to know themselves more truly and personal transformation can occur. Jung made significant step of defining the unconscious of a person as comprised of both: personal unconscious-proceeding from the experiences of the individual, and a collective unconscious-issuing from the inherited structure of the brain, and common to humanity. The unconscious, the inner "environment" of the psyche, is a different medium from the conscious.
According to C. G. Jung dream analysis is the primary way to gain knowledge of the hidden part of our mind.