 The question of whether classical, Mendelian genetics could be (or already has been) reduced to molecular biology (to be taken up in  Section 3.1  below) motivated philosophers to consider the connectability of the term they shared: the gene. Investigations of reduction and scientific change raised the question of how the concept of the gene evolved over time, figuring prominently in C. Kenneth Waters’ (1990, 1994, 2007, see entry on  molecular genetics),  Philip Kitcher’s (1982, 1984) and Raphael Falk’s (1986) work. Over time, however, philosophical discussions of the gene concept took on a life of their own, as philosophers raised questions independent of the reduction debate: What is a gene? And, is there anything causally distinct about DNA? (see the entry on the  gene)