 Scheibe in his (1999) also explicitly refers to the theses of Kuhn and Feyerabend and gives a detailed discussion. Unlike the other two structuralistic programs, he does not propose a fixed concept of reduction. Rather he suggests a lot of special reduction relations which can be combined appropriately to connect two theories \(T\) and \(T'\). Moreover, he proceeds by means of extensive real-life case studies and considers new types of reduction relations if the case under consideration cannot be described by the relations considered so far. Scheibe concedes that there are instances of incommensurability which make it difficult to find a reduction relation in certain cases. As a significant example he mentions the notions of an “observable” in quantum mechanics on the one hand, and in classical statistical mechanics on the other hand. Although there are maps between the respective sets of observables, Scheibe considers this as a case of incommensurability, since these maps are not Lie algebra homomorphisms, see Scheibe (1999, 174). 