The concept of the id vs. super-ego, with the ego as intermediary, served as a source of much contemplation for Jung. He eventually came to expand greatly on this matter, changing the face of psychology forever.

He argued that the super-ego is not separate from the ego; he termed that part of our ego so dedicated to fitting into society's set of expectations the persona - our mask to the outside world. The persona is distinct from the super-ego in that the former is part of consciousness while the super-ego was said to be partly unconscious.

 Jung realised that there is indeed a part of us that holds the values of parental figures and society at large. He also saw another part of us that could enlist the aid of the ego to counter the demands of the persona. This element, which he termed the Self, is that part of the unconscious that compels us forward.

The Self can recognise those demands of the persona that are inhibiting inner evolution; the reality-orientated part of the ego then becomes the unfortunate tool of both.

Jung's research into libido also brought him to the conclusion that the unconscious is two-fold; that is, that we have a personal unconscious (the sum of all our experiences in life) and a collective unconscious.

He realised that the images that invade our thoughts are largely universal. These primordial images he called archetypes, and he saw them as arising from the collective unconscious, which he viewed as the sum of all past human experience. The fact that mankind shares these archetypes is evident in the striking similarities between religious symbolisms of cultures that were isolated from one another.

For example, the symbol of the mother has meant shelter, protection and nourishment to many cultures; similarly, the father image has symbolised power, authority and the creative spirit.

Jung argued that archetypes, so often projected onto people or things in our environment, are instrumental in our psychological evolution. Archetypes give us a chance to recognise fairly inaccessible parts of our unconscious. To see this in action, we must look to Jung's model.

In simple terms, Jung's model was this: an unrecognised element of the unconscious - be it a repressed trauma or desire, an instinctual need for comfort and pleasure or the drive to achieve in life - is urged by the Self to call out to consciousness; the personal unconscious sends its libido into consciousness, usually accompanied by an archetype from the collective unconscious; the ego tries to cater to the needs of the unconscious, but often finds conflict with the persona; the persona pushes the impulses back to unconsciousness.

A basic example of this would be the young man whom is invaded by archetypes of power and authority. He misinterprets the true message - which may be a call for the boy to progress positively in school and in his environment - and thus becomes a schoolbully. Alternatively, his persona (developed amongst his peers) may rebel against the impulses that are compelling him towards adulthood and cause him to rebel against authority figures, such as teachers. The true nature of the libido is left unrecognised.

After a while, Jung came to see the libido as not only moving forwards (progression) and backwards (regression) but also inwards and outwards. He coined the terms extraverted and introverted and helped define the ways in which people can progress and regress.

The progression of libido (or adaptation to outer conditions) can occur in two ways: extraverted, when the progression is influenced by objects and environmental conditions; and introverted, when the progression has to adapt to the conditions of the ego.

The regression of libido (or adaptation to the inner conditions) can similarly proceed in two ways: extraverted, manifest as "a flight into extravagant experience of the outside world"; and introverted, being retreat from the outside world.

"The process of energic transformation or conversion" he termed the canalization of libido, viewing it as "a transfer of psychic intensities or values from one content to another, a process corresponding to the physical transformation of energy".