 A similar criticism of reduction involves a different move: that the deductive connection be guaranteed provided that the old, reduced theory was “corrected” beforehand (Shaffner 1967). The evolution and the structure of scientific knowledge could be neatly captured, using Schaffner’s expression, by “layer-cake reduction.” The terms “length” and “mass”—or the symbols \(l\) and \(m\)—, for instance, may be the same in Newtonian and Relativistic mechanics, or the term “electron” the same in classical physics and quantum mechanics, or the term “atom” the same in quantum mechanics and in chemistry, or “gene” in Mendelian genetics and molecular genetics (see, for instance, Kitcher 1984). But the corresponding concepts, they argued, are not. Concepts or words are to be understood as getting their content or meaning within a holistic or organic structure, even if the organized wholes are the theories that include them. From this point of view, different wholes, whether theories or Kuhnian paradigms, manifest degrees of conceptual incommensurability.  As a result, the derived, reducing theories typically are not the allegedly reduced, older ones; and their derivation sheds no relevant insight into the relation between the original, older one and the new (Feyerabend 1962; Sklar 1967).