>I’m reasonably sure we can rely on the linear nature of time. I'm not even sure about that, perhaps we can rely on our linear _experience_ of time, but we can

>I’m reasonably sure we can rely on the linear nature of time. I'm not even sure about that, perhaps we can rely on our linear _experience_ of time, but we can't determine which is the correct version of two billiard balls colliding if we're shown the forwards and the backwards versions. Assuming time is linear is convenient, but I don't think its provable or outright definite.