Phenomenological Realism, Superconductivity and Quantum Mechanics

"As Towfic Shomar argues, if we are looking for quantum description that gives very accurate predictions about superconducting phenomena we can make do with the "phenomenological" equations of Ginzburg-Landau model, These equations are phenomenological in two senses: First, they are not derived by constructing a model to which a Hamiltonian is assigned, but rather are justified by an ad hoc combination of considerations from thermodynamics, electro-magnetism and quantum mechanics itself. Second, the model does not give us any representation of the causal mechanisms that might be responsible for superconductivity." Nancy Cartwright, from her book: "The Dappled World", CUP, Cambridge 1999, pp 193-4.