 One suggestion to make sense of the possibility of the supervening functional explanations without Nagelian reduction is a metaphysical picture of composition of powers in explanatory mechanisms (Gillette 2010). The reductive commitment to the lower level is based on relations of composition, at play in epistemological analysis and metaphysical synthesis, but is merely formal and derivational. We infer what composes the higher level but we cannot simply get all the relevant knowledge of the higher level from our knowledge of the lower level (see also Auyang 1998).  