At the Schrodinger's equation level, quantum mechanics is completely deterministic. The probabilistic nature of QM only kicks in when measurements and wavefunction collapse take place. So does this mean that the portion of the universe outside the particle horizon is free from quantum indeterminacy, since we cannot perform measurements on it? The only problem I see is that if entanglement (due to causal decoupling from inflation) between observable and unobservable universe exists, then measurements on the observable universe can cause wavefunction collapse in the unobservable universe. However, the assumption is that quantum non-locality can penetrate the barrier of GR causal separation. Is this generally considered valid? At a more exotic level, can we claim that the universe would be completely deterministic if there were no intelligent life forms, because no measurement would ever takes place? I suppose the answer to this question is interpretation-dependent?