Grandfather Paradox, and more

[zedro]

We are not in an "anything goes" reality, there are nodal points (deterministic realities which intersect choices) which need to be maintained to have a cohesive universe. Think of it like a video game, there are a lot of transient actions which can take place, but the overall plot needs to make sense to keep the illusion from falling apart. So some actions simply cannot happen, as the option will not even present itself. This is a system bound by rulesets, which is why some who witness the "bugs" in the program get removed from the game in some form.