In "The Significance of Constitution and Heredity in Psychology" (November 1929), Jung wrote:
"And the essential thing, psychologically, is that in dreams, fantasies, and other exceptional states of mind the most far-fetched mythological motifs and symbols can appear autochthonously at any time, often, apparently, as the result of particular influences, traditions, and excitations working on the individual, but more often without any sign of them. These "primordial images" or "archetypes," as I have called them, belong to the basic stock of the unconscious psyche and cannot be explained as personal acquisitions. Together they make up that psychic stratum which has been called the collective unconscious.
The existence of the collective unconscious means that individual consciousness is anything but a tabula rasa and is not immune to predetermining influences. On the contrary, it is in the highest degree influenced by inherited presuppositions, quite apart from the unavoidable influences exerted upon it by the environment. The collective unconscious comprises in itself the psychic life of our ancestors right back to the earliest beginnings. It is the matrix of all conscious psychic occurrences, and hence it exerts an influence that compromises the freedom of consciousness in the highest degree, since it is continually striving to lead all conscious processes back into the old paths."