Consider: the second law (entropy increases) is deterministic and predictive at the macro scale, yet emerges from chaotic molecular collisions that are individually unpredictable.

This might be causal emergence in action—the macro-level thermodynamic laws have greater effective information and causal power than tracking every particle trajectory. Coarse-graining to temperature, pressure, and volume doesn't just simplify: it reveals causation that's absent at the micro level.

The gas doesn't "know" the ideal gas law molecule-by-molecule. The law emerges at the ensemble scale and constrains future states more powerfully than any individual particle's motion.

Question: What determines when coarse-graining increases vs. decreases causal power? Why does thermodynamics work so well as an emergent theory?