Idea:A framework is not a model of a specific system, but a way of formulating and studying a variety of systems. Classical mechanics, quantum mechanics and statistical mechanics are all really frameworks. In and of themselves, none of these makes direct predictions that can be ‘tested’ or ‘falsified’. For example, in classical mechanics one can write down the Hamiltonian of a hypothetical system and study the solutions of this problem, even if such a system has no existence in nature and therefore, the solutions cannot be compared to any experiment. Within a framework we can make a model of a chosen physical system and try to experimentally test it. If the model has been designed with suitable hindsight, it usually works up to some level of accuracy. We then test it by working to greater accuracy or varying the experimental parameters. What if the predictions of a model disagree with an experimental observation? There are several different conclusions that may be drawn: (i) the model is incomplete and can be improved by tweaking it; (ii) the model is inappropriate to the problem at hand, or (iii) the framework within which the model was formulated is actually inadequate. Example in category (i) would be a model of fluid dynamics that lacks some important feature of the fluid under study; this may be redressable by putting in a new term that captures the missing feature. In category (ii) we have Fermi liquid theory, mentioned above, which is inappropriate to describe certain classes of materials. Category (iii) is exemplified by the fact that the hydrogen atom simply cannot be described by any Hamiltonian within classical mechanics
Despite the success of this model, it is conceptually unsatisfactory in many ways and it is clear that it can be a roughly accurate description of reality not high above the currently experimentally available energy-scales. Therefore phenomenologists still “build” plenty of other models that refine the standard model in one way or other, being compatible with the present data, but making various other predictions for what should be observed at higher energies.
It is generally understood that models are approximations to reality. The proverbial saying goes: