Wasserman presents a common argument against time travel:
(P1) If backward time travel were possible, it would be possible to perform a self-defeating act.
(P2) It is impossible to perform a self-defeating act.
(C) Backward time travel is impossible.
If one finds one example of a universe where backward time travel is possible and it is not possible to change the past, does this mean that time travel is possible?
(By time travel is possible in the universe, I mean there exist closed timelike curves in the universe (definition of time travel used by Smeenk and Wuthrich, 2011)