  Wimsatt, Kitcher, and Sarkar seek to replace Nagel's conception of reduction with a conception that does not assume that scientic explanation involves subsumption under universal laws. Weber (2005), however, seeks to replace Nagel's conception with one that retains the idea that reductive explanation involves subsumption under laws of the reducing science. What Weber rejects is the idea that reductionism in biology involves explaining higher-level biological laws. He argues that, with some rare exceptions, biological sciences don't have laws. He contends that reductionism in biology involves explaining biological phenomena directly in terms of physical laws. Hence, he rejects the "layer-cake" conception of reduction implicit in Nagel's account.