As implied in the previous part of this analysis, the blue box is symbolic of Diane's Self, which is the final stage of the process of individuation. According to Jungian psychology, individuation is a process of psychological integration, having for its goal the development of the individual personality. "In general, it is the process by which individual beings are formed and differentiated; in particular, it is the development of the psychological individual as a being distinct from the general, collective psychology. Individuation, therefore, is a process of differentiation, having for its goal the development of the individual personality."[a]
Prominent Jungian archetypes involved in the stages of the individuation process are the shadow, the Wise Old Man and the Wise Old Woman, and the anima in man and the animus in woman.
Individuation is a process of transformation whereby the personal and collective unconscious is brought into consciousness (by means of dreams, active imagination or free association to take some examples) to be assimilated into the whole personality. It is a completely natural process necessary for the integration of the psyche to take place. Individuation has a holistic healing effect on the person, both mentally and physically.[b]
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The cheerful Betty Elms represents Diane Selwyn's 'dream-persona'.
Diane's persona is represented in her dream by Betty. (When it was suggested in part 10 that Betty represents Diane's ego, this meant within the context of her being absent when Rita opens the blue box - this symbolizes the ego submitting to the Self.) Louise Bonner represents the Wise Old Woman, and the person behind Winkie's represents Diane's shadow. Actually, the person behind Winkie's appears as a man to Dan, but he/she represents a woman for Diane - the shadow is generally same-sex.
a. Jung, C.G. The Collected Works of C.G. Jung, Vol. 6. Princeton University Press, 1971. para. 757.
b. Wikipedia, 'Individuation'. Web, n.d. URL = https://en.wikipedia.org/wiki/Individuation.