Many attempts to interpret quantum mechanics do so by looking at three nested systems. The largest system is essentially the universe or the environment. The smallest system is the one being observed and following the laws of the theory, and the middle system contains the measurement device or the observer.
At least Schrödinger remarked in his famous article with the cat that properties of bosons and fermions might make this setup questionable (even if he wasn't very committal about whether bosons and fermions are really the last word), because they don't seem to allow for such a clear separation.
But because already interpretation of probability theory can cause controversies, I wonder whether this same setup with three nested systems could also be used to interpret classical probability theory. And one might also try to interpret the classical static deterministic and causal theory with this setup, after all even the interpretation of causality might cause controversies. But why should one expect to learn anything at all about causal or probabilistic theories, by looking at three nested systems? Is this because we can see ourselves as being in the middle between the universe and what we observe, or has this setup something to do with quantum mechanics itself, or is this setup simply misguided?
