It's not that the universe might "literally" prevent you from performing an action. It's just that our universe doesn't allow it in the first place. The coheren

It's not that the universe might "literally" prevent you from performing an action. It's just that our universe doesn't allow it in the first place. The coherence of the universe is a biproduct of its inherent order. I guess what I mean, without sounding too pseudo-scientific, is I believe the way it works is that, if, say, you go back in time and kill your grandfather, then what is actually happening is you are killing the person you thought was your grandfather, but they were not, in fact, your grandfather to begin with. In fact, all you would know going back is that your grandfather was murdered by someone. Let's say you believe it was you, and you have a change of heart. Decide it's not in you to kill someone, even to prove a scientific point. That doesn't mean he doesn't get killed. Nothing's changed. It's simply that someone else killed him. The answer to the question of Schroedinger's cat isn't that the cat is dead or alive, it's that it is.