Possibly one of the oddest closing sentences of a technical book – and a very good one at that – I’ve ever read:
This pressure can be calculated by minimizing the Helmholtz function of the system. Details can be found in Fermi’s textbook on thermodynamics (Fermi 1956). But why does osmosis explain the behavior of a salted cucumber? This question is left to the reader as a parting gift.
-André Thess in The Entropy Prinicple: Thermodynamics for the Unsatisified, Springer 2011