Comment by bee_rider

There's nothing really "not actually possible" about Maxwell's Demon. It is maybe impractical from an engineering point of view to create the demon, but this doesn't resolve the problem, which is based in the more fundamental physics. I think a more accurate description of the resolution is that this "deciding what to do on the micro level" must itself have an energy cost -- making it a great example of the link between information and thermodynamic entropy.