"All those qualities, capacities and tendencies which do not harmonize with the collective values – everything that shuns the light of public opinion, in fact – now come together to form the shadow, that dark region of the personality which is unknown and unrecognized by the ego.

The endless series of shadow and doppelgänger figures in mythology, fairy tales and literature ranges from Cain and Edom, by way of Judas and Hagen, to Stevenson’s Mr. Hyde in the ugliest man of Nietzsche; again and again such figures have appeared and made their bow before human consciousness, but the psychological meaning of this archetype of the adversary has not yet dawned upon mankind.”

- Depth Psychology and a New Ethic by Erich Neumann