"I" and "Not I"

The double, both in literature and out of it, is an enormous and seductive subject. As an imagined figure, a soul, a shadow, a ghost or a mirror reflection that exists in a dependent relation to the original, the double pursues the subject as his second self and makes him feel as himself and the other at the same time. While its imaginative power springs from its immateriality, from the fact that it is and has always been a phantasam, the psychological power of the double lies in its ambiguity, in the fact that it can stand for contrast or opposition, but likeness as well.

M. Zivokvic, The Double as the "Unseen" of Culture: Towards a Definition of the Doppelganger Linguistics and Literature Vol.2, No 7, 2000 p. 122