Doppelganger. Interestingly, my dictionary give is tithe the umlaut on the "a". I have
some distaste for its omssion. Here a quate from the net:
Since the doppelganger motif was introduced into Romantic literature by Jean Paul Richter in Siebenkas (1796), writers have mainly focused on the duality within male characters when employing literary doubles. Goethe, Chamisso, E.T.A. Hoffmann, Dostoevsky, Poe and Borges are among the most well-known authors whose works have made effective use of the double but predominantly from the point of view of the male protagonist and his psychological make-up.

From the X-bonus: The DelaRochefoucauld Maxime I like best: The refusal of praise is merely the desire
'to be praised twice.