quote:
A is cause. B is the effect of the cause A.
A causes B.
B is the action of going back in time and preventing A from happening.
A never happened, therefore B never happened. But if B never happened, then A did happen, meaning B did happen. But if B did happen then A didn't happen. But A is the cause of B so then B didn't happen. But if B didn't happen then A did happen which means B did happen.
When you travel back and change the history you spilt off into an alternative timeline - isn't that the standard answer to that problem?