   This account covers interlevel theory reduction. For instance, Oppenheim and Putnam (1958) argued for a hierarchical or layered model of scientific disciplines that assumes each layer or level corresponds to a theory. Each discipline is reducible to the theory on the next lower level, e.g., sociology to organismal biology, organismal biology to molecular biology, molecular biology to chemistry, and chemistry to microphysics (see also Brooks 2014, Hüttemann and Love 2016, Walter and Eronen 2011). Another way to apply Nagel’s general model is successional theory reduction, where a historically earlier theory is reduced to a later, more mature theory, so that reduction can be an instance of theoretical progress (Nickles 1973). In both cases Nagel held that theories needed to be indexed to a particular time: “The question whether a given science is reducible to another cannot in the abstract be usefully raised without reference to some particular stage of development of the two disciplines” (1961, 361).  Paul Feyerabend  (1962, 1965a, 1965b) and  Thomas Kuhn  (1962) criticized successional theory reduction and especially Nagel’s connectability condition. Feyerabend argued that an earlier and later theory might use the same theoretical term with a different meaning (e.g., “mass” in classical and relativistic mechanics). This  incommensurability  of meaning makes the connectability of these theories’ expressions, and thus the logical derivation of one theory from another, impossible. Whether or not genuine incommensurability obtains is controversial (see, e.g., Sankey 1994).