When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time. ("P" stands for "Proposition" and "C" stands for "Conclusion") Here we go: P1: I did not exist in 1776. P2: I exist now in a reality that includes P1 as being true. P3: I go back in time (using whatever means) to 1776. C: I did exist in 1776! ... But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound? Any and all helpful criticism is appreciated.