Compositional Explanatory Relations and Mechanistic Reduction

Recently, some mechanists have embraced reductionism and some reductionists have endorsed mechanism. However, the two camps disagree sharply about the extent to which mechanistic explanation is a reductionistic enterprise. Reductionists maintain that cellular and molecular mechanisms can explain mental phenomena without necessary appeal to higher-level mechanisms. Mechanists deny this claim. I argue that this dispute turns on whether reduction is a transitive relation. I show that it is. Therefore, mechanistic explanations at the cellular and molecular level explain mental phenomena. I make my case in part by noting that mechanisms at higher levels are composed of mechanisms at lower levels. Compositional relations are transitive. In addition, they are explanatory. I conclude that there are explanatory linkages from cellular and molecular mechanisms to mental phenomena within a hierarchy of nested mechanisms.