[wnkrshm]

Even in a perfectly deterministic universe, the accessibility of that determinism to models hinges on knowledge of the state of the universe.

We're surrounded by highly nonlinear interactions that we just approximate as linear - if we want to truly predict anything, in general, we'd need infinite precision on the variables that describe the state of these systems, because an infinitely small perturbation in the initial conditions can cause an almost (limited by conservation laws) arbitrary deviation in the predicted state.