Quote: "Because if you accept that the man went back in time you accept the fact there are parralel worlds spaced out 1unittime/sppacetime apart"
No.
Quote: ""I know I know nothing" - this, I believe, is an example of a paradox."
It's not, because if it is a lie, then he does not know that he knows nothing, just like everyone else in the world.
"This statement is a lie" is different. Because if it is a lie, then it is not a lie and thus is the truth, and if it is the truth then it is a lie. A loop and a logical impossiblity. Unlike almost all the other examples here
Edit-- I do admit that the time 'paradox' I mentioned does take for granted you buy into a certain theory of time travel. Nevertheless it's fun to think about.
--Mouse: Famous (Avatarless) Fighting Furball
I am the chainsaw paladin.