It seems to be quite widely assumed (I am informed, by sources who read more about this sort of thing than I do) that backwards time travel requires backwards causation. It wouldn't suffice for time travel if in 2015 I climbed into a time machine and someone looking and acting exactly like how I look in 2015 came into existence for no apparent reason in 1926. Rather, that person's turning up in 1926 would have to be caused by my actions in 2015.
I agree with the insufficiency claim. But I'm not sure whether the causal requirement is motivated by it. (I'm also hung up on whether it might be a conceptual truth that causation happens forwards, not backwards, but let's not worry about that.) Wouldn't it be enough if there were the right kind of non-casual explanation of this person's turning up in 1926, in terms of my actions in 2015? If not, why not?
(I am concerned that I will be trussed up in a sack and sent back to Cambridge for posting on this, but I'm going to do it anyway ...)