paradoxes in science fiction

A paradox is a curious thing, because paradoxes seem to emerge out of thin air.
The classic linguistic paradox is the sentence, This statement is false. If it's false, then it must be true, which means it's false, etc. The weird thing is that although someone, somewhere first invented that paradox, it has the feel of something that was already there, out there, waiting to be discovered rather than invented.
Philosphers have noted that paradoxes arise out of being an observer, a commentator trying to describe reality, rather than just an object in the universe. This statement is false works as a paradox because it is an attempt by an observer -the person who wrote the sentence- to describe one small piece of the universe: the sentence itself. In doing so, it turns in on itself, leading to a linguistic hall of mirrors.
Science fiction is fertile ground for the exploration of paradoxes, because of the ability to explore the boundaries of observation. In particular, the tools with which science fiction writers explore paradoxes are time travel (observing time in a non-linear sequence); androids (machine observers); and symbiosis (where the boundary between observers becomes blurred).
Philip K Dick is one science fiction writer who loved to explore paradoxes in his writing. He is, I believe, the heir to Joseph Heller. I recently posted an essay on paradoxes in the work of Philip K Dick at pkdick.com. Philip K Dick uses paradoxes, catch-22's, and contradictions to trap his characters, and to force them to confront their own mortal boundaries.