Although I have no objection to accepting the existence of relatively constant psychic contents that survive personal ego, it must always be born in mind that we have no way of knowing what these contents are actually like "as such." All we can observe is their effect on other living people, whose spiritual level and whose personal unconscious crucially influence the way these contents actually manifest themselves.

"Modern Examples of Background Physics" ["Moderne Beispiele zur Hintergrundsphysik"] (1948) as translated by David Roscoe in Atom and Archetype (1992) edited by Carl Alfred Meier