Are More Details Better? On the Norms of Completeness for Mechanistic Explanations

Completeness is an important but misunderstood norm of explanation. It has recently been argued that mechanistic accounts of scientific explanation are committed to the thesis that models are complete only if they describe everything about a mechanism and, as a corollary, that incomplete models are always improved by adding more details. If so, mechanistic accounts are at odds with the obvious and important role of abstraction in scientific modelling. We respond to this characterization of the mechanist's views about abstraction and articulate norms of completeness for mechanistic explanations that have no such unwanted implications.