>>87781614Have you hear Larry Niven's "Strong Theory Against Time Travel" ? it's specific to time travel that can alter the past and thusly alter the 'present'. It's a theory that uses induction.
Let's propose that past-altering time travel exists. This means anybody with a time machine (an "agent") can jump down the timeline, make changes, and it will alter the present-day with nobody knowing about it except the agent of change. It's like events are stacked one on top of another, and by moving a bottom event all the events above it are yanked away. But another agent can do the same, perhaps jumping behind the first agent to change what their new present-day history books record. (q.f.: "Killing Hitler As A Baby" cliché). Any agent's changes will wipe out any other agent's change in a point of time above their jump, although other agents in the new timeline could jump down a few more steps and make changes and the new "present day" at the top of the would be none the wiser.
This keeps happening ("i warned you about time-travel bro!"), with the past in constant flux from new time machines and agents messing with lower and lower steps of the temporal staircase, until one crucial event is prevented: the invention of the time machine. You prevent the time machine, you prevent agents, and you prevent anyone who could jump behind you and undo what you did. Until time travel is invented at a later date, then the whole mess goes into flux again, until another agent prevents time-travel again.
The thing is, all of us who aren't that one agent that prevented time travel, we're in the "present day", so are only memory and history is the current timeline, the one after the agent did their meddling. So we will only every remember a history where time-travel is "impossible" because any other timelines are constantly in flux, with us remembering whatever as the time-travel agent pile doesn't stop getting taller... until one of them prevents time travel again.
