Page "Novikov self-consistency principle" Paragraph 28

* Robert A. Heinlein's By His Bootstraps ( 1941 ) features a plot in which a man interacts with different older versions of himself that travel by way of a " Time Gate ", with all the interactions revisited later in the story from the perspective of the now-older man, everything being tied together in a completely self-consistent way.

Heinlein later revisited a similar theme in his 1958 story — All You Zombies —, in which the main character's interactions with sex-changed versions of himself / herself at various points in his / her life result in a bizarre version of the ontological paradox in which the character becomes his / her own mother and father.