 In the writings of Ludwig there is no direct reference to the incommensurability thesis and the corresponding discussion. But obviously his approach implies the most radical denial of this thesis. His reduction relation is composed of two simpler intertheoretic relations called “restriction” and “embedding”. They come in two versions, exact and approximate. Part of their definitions are detailed rules of translation of the non-theoretic vocabulary of \(T'\) into that of \(T\). Hence commensurability, at least on the non-theoretical level, is insured by definition. The problem is then shifted to the task of showing that some of the interesting cases of reduction, which are discussed in the context of incommensurability, fit into Ludwig’s definition. Unfortunately, he gives only one extensively worked-out example of reduction, namely thermodynamics vs. quantum statistical mechanics, in Ludwig (1987). Incommensurability of theoretical terms could probably be more easily incorporated in Ludwig’s approach since it could be traced back to the difference between the laws of \(T\) and \(T'\). 