The molecular and fluid descriptions of air in a room provide an innocent, uncontroversial example of emergence. Everyone agrees on what is happening and how to talk about it. But its simplicity can be misleading. Seeing how relatively easy it is to derive fluid mechanics from molecules, one can get the idea that deriving one theory from another is what emergence is all about. It’s not—emergence is about different theories speaking different languages, but offering compatible descriptions of the same underlying phenomena in their respective domains of applicability.
