Most theories about temporal paradoxes, retro-causality and time can get pretty complicated.
Wikipedia outlines many current philosophical positions on temporal paradoxes, so rather than go nuts by trying to rewrite what’s been said there, I’ll just link to it:
If you’ve at least scanned over what Wikipedia says, read on…
I think a lot of the current thinking about temporal paradoxes, retro-causality and time is flawed because, on the one hand, thinkers talk about going back in time, but on the other hand, they continue to philosophize as if time suddenly becomes linear again, once you’ve gone back in time.
From what we see in the latest new physics experiments, time is more like a multidimensional patchwork quilt. This means, if I can put it simply, that all of time is always interactive.
One of the analogies I sometimes use when trying to explain my view of time is to say that it’s like a ball of spaghetti, with each strand of spaghetti being a kind of wormhole cutting through and connecting different moments and places in time.
We cannot time travel on the macro level. We have no time machines. As much as I’d love to, I can’t go back to, say, New York City in the 1930s or to ancient Rome at the time of Caesar. But some subatomic particles do appear to time travel. And we have repeatable scientific experiments to support this.¹
Also, some report experiencing a kind of psychological – if not large-scale physical – time travel, especially when entering into deeper, meditative states of awareness.²
As for ethics and time travel, in the TV show Star Trek, which often involves the idea of time travel, the following hypothetical problem arises:
If a person had to choose between influencing two or, perhaps, more possible historical outcomes while traveling back in time, how would she or he know which choice would be right?
One might say that the best ethical choice would be right. But even those of us stuck in the present know that “right ethics” are not always easy to determine.
One hypothetical solution to this equally hypothetical problem involves the idea that every time we make a choice, a new universe branches off, creating a potentially infinite number of universes for each choice we make.
Again, there are several other theories about time travel mentioned at Wikipedia. It’s beyond me to go into each one, especially when I feel that most of them are loaded with faulty assumptions from the outset.