I was playing with this recently. Suppose you are playing rock, paper, scissors with yourself from a few minutes into the future. Your future self “remembers” what you will play and so as long as you play normally, future self always wins. But change the rules a bit and play where future you goes first.

In a normal game, you should always win because you clearly see how future you played, but future you played to counter what future you remembers present you playing…

E.g. future you remembers playing paper, and so plays scissors. You see scissors and go go play rock, but that should be impossible because future you doesn’t remember playing rock.

The weird thing to me is not that the second scenario (where future you goes first fails) but that playing normally (both going at the same time) works. I think the paradox emerges when future knowledge is introduced to the past. In the normal game, future you does not expose future knowledge until the exact moment you play and cause that knowledge to exist in your present, but in the altered game, the introduction of future knowledge creates a feedback loop.

Of course the game isn’t needed. Simply seeing future you conveys the fact that you exist in the future. Should you, for example (and please don’t do this) see near future you then stab your arm with scissors, you will miss or be stopped because future you does not have a wounded arm.

I wonder what happens if future you’s arm is out of sight. would you be able to stab your arm then only for future you to then reveal a wounded arm?