Carl Gustav Jung's idea of the collective unconscious is first and foremost based on the ideas presented by Freud. Freud suggested a triadic model of the subject which is composed of the ego, id and super-ego. This structure is based on the distinction between the conscious, unconscious and preconscious, known as Freud's topographical model of the mind. Freud held that we take memories, fantasies and mental content that we cannot cope with and divert them into the unconscious, a process he termed as repression. Freud noted to levels of the unconscious, the universal one –"phylogenies", and an individual one –"ontogenesis". The universal unconscious contains inherited repressions which are termed by Freud as "primary repression" which has according to him 3 main fantasies: castigation, temptation and primal scene.
The personal process of repression is termed by Freud as "secondary repression" which exiles unpleasant thoughts to the unconscious, there they do not vanish but rather become separated from the conscious level. Repressed content reappears in a distorted and sublimated form in dreams, jokes, slips of tongue and of course psychological pathology and neurosis.
Unlike Freud, Jung held that the unconscious has positive sides as well. Freud thought that psychotherapy should discover repressed content in order to process it and reconcile with it. Jung thought that the unconscious also has locked-away "resources" that their discovery might aid in achieving mental balance.
Dreams were a central subject for dispute between Freud and Jung, a dispute which eventually led them to break up their friendship. Freud did have some interest in what he called Phylogenies and universal fantasies in order to interpret the human psyche, but he was more focused on personal private content since his theory revolved around the subject's relation with the other (object). Jung, on the other hand, was more interested in the subject's relations with himself, and this made him pose the idea of the collective unconscious at the center of his psychoanalytic theory. Therefore, for Jung and unlike Freud, dreams do not necessarily point to our relations with the other but can also contain various aspects of our own psyche. Repression, in other words, does not deny something about our relation with the world, as Freud argued, but rather something about our relation with ourselves that once freed can lead to mental harmony.