What little we remember

The status of phenomenological models is considered and it is argued that they should not be taken as approximations to more fundamental treatments only. To be useful they should work in a consistent world of concepts and their observational manifestations. In this situation, the border between phenomenological theories and fundamental laws is blurred. Within these frames, we discuss the derivations of irreversible master equations when memory effects are significant. In schematic frameworks of derivations, the emergence of irreversibility is followed, and various levels of approximations are presented. Full memory and time-local forms are considered before the Markovian result emerges. The validity of the approximations is discussed.