Logic And Time Travel

"'How does time travel work, anyway? Impossible and absurd, I've read.'

"He nodded. 'According to today's physics and logic, that's true. They'll learn better in the future."

-Poul Anderson, The Shield Of Time (New York, 1991), 1987 A. D., p. 27.

Time travel is not impossible according to logic which is merely consistency between propositions and is equally necessary whether we are discussing hypothetical time travel or anything else. Example: a man begins a lecture on Greek philosophy by stating that Socrates was executed in 399 BC and ends his lecture by reminding us that Socrates was executed in 299 BC. When challenged on the inconsistent dates, he apologizes for a slip of the tongue and clarifies that 399 BC is the correct date. However, imagine that, instead, he says, "I transcend logic and am entitled to contradict myself." No one does say such a thing and, if anyone did, then he would not succeed in telling us when Socrates was executed. There is no contradiction between the statements that I appeared in ancient Greece and that I disappeared in contemporary Britain.