Oh, almost forgot:

>>Can they really be said to exist?
> Yes, we can. We can see the effects of their existance.

Actually, we can't - measuring the state of the system at any point is equivalent to knowing its state at any earlier or later time, and we can't do that. We can't measure the initial condition, and we can't measure the later condition either. It remains forever out of reach.

We can see that something happens, but we can't tell exactly what at any time.