 A functional mechanism is a system of organized components, each of which has functions to perform (cf. Craver 2012, Garson 2013). When appropriate components and their functions are appropriately organized and functioning properly, their combined activities constitute the capacities of the mechanism. Conversely, when we look for an explanation of the capacities of a mechanism, we decompose the mechanism into its components and look for their functions and organization. The result is a mechanistic explanation of the mechanism’s capacities.