 Kenneth Schaffner (1967, 1969) further develops Nagel’s account by pointing out that the candidate reduced theory typically needs to be corrected before it can be reduced. He then applies his model to the case of genetics. On Schaffner’s view, molecular genetics reduced or is in the process of reducing classical genetics (see  §1.2  and  §1.3  for an account of classical and molecular genetics). On his account, the genes of classical genetics can be identified with DNA sequences. Furthermore, concepts that capture law-like generalizations about phenomena in classical genetics (e.g., dominance) can be explained through generalizations on the molecular level. Schaffner’s account is met with criticism by David Hull (1972, 1974). Hull’s most influential objection rests on a multiple realizability argument. He argues that the types of phenomena identified in classical genetics (such as dominance) can be instantiated by a variety of different molecular constellations. Furthermore, Hull points out that any molecular entity or mechanism can be involved in various types of situations as described in classical genetics. Accordingly, Hull diagnoses many-many relations between molecular phenomena and phenomena identified through cytological and phenotypic analysis.