Role of thermodynamics in multiscale physics

One way to deal with complexity is to recognize important features, concentrate on them, and ignore everything else. A useful strategy for the recognition process is to carry out the investigation on several levels involving different amounts of detail and then compare the results. The comparison is, in its essence, thermodynamics. We formulate such abstract thermodynamics (we call it the Dynamical Maximum Entropy Principle) and show that the equilibrium and nonequilibrium thermodynamics as well as the equilibrium and nonequilibrium statistical mechanics are all its particular representations.