  The abstract level of discourse began with Schaffner's idea that what is reduced is not the original theory, but rather a corrected version of the original theory.  Wimsatt (1976a) offers a more ambitious modification. He rejects the assumption that scientific theories are sets of law-like statements and that explanations are arguments in which the phenomena to-be-explained are derived from laws. Instead of relying on these assumptions, Wimsatt uses Salmon's account of explanation (Salmon 1971) to examine claims that molecular genetics offered reductive explanations. Kitcher (1984) also rejects the account of theorizing underlying Nagel's concept of reduction. He constructs a new concept of reductive explanation based on his own idea of what effectively constitutes a scientific theory and his unificationist account of scientific explanation (1989). Likewise, Sarkar (1998) rejects the account of theories and explanation presupposed in Nagel's concept of reduction. In fact, he explicitly avoids relying on any particular account of scientific theories or theoretical explanation. Instead, he assumes that reductive explanations are explanations without specifying what an explanation is, and then seeks to identify the features that set reductive explanations apart from other explanations.