 Philosophy of biology first came to prominence as a sub-specialty of philosophy of science in the 1970s when it offered an apparent case study by which to judge how theories from one field may reduce to theories from another field. The specific question was: might classic, Mendelian genetics reduce to molecular genetics (see the entry on  genetics  and --> molecular genetics)?  Kenneth Schaffner used and developed Ernst Nagel’s (1961) analysis of derivational theory reduction to argue for the reduction of classical Mendelian genetics (T2) to molecular biology (T1) and refined it over many years (summarized in Schaffner 1993). The goal of formal reduction was to logically deduce the laws of classical genetics (or its improved successor, “modern transmission genetics” T2*) from the laws of molecular biology. Such a derivation required that all the terms of T2* not in T1 had to be connected to terms in T1 via correspondence rules. Hence, Schaffner endeavored to find molecular equivalents of such terms as “gene”, as well as predicate terms, such as “is dominant”. David Hull (1974) criticized formal reduction, argued against Schaffner’s claims, and suggested, instead, that perhaps molecular biology replaced classical genetics.