Whether the analysis succeeds depends on how one deals with the resulting regress (Craver 2007). As Glennan (2009) notes, the decomposition of causes into mechanisms might continue infinitely, in which case there is no point arguing about which notion is more fundamental, or the decomposition might ground out in some basic, lowest-level causal notion that is primitive and so not analyzable into other causal mechanisms. The latter option must confront the widely touted absence of causation in the theories of fundamental physics (Russell 1913); at very small size scales, classical conceptions of objects and properties no longer seem to apply, making it difficult to see what content is left to the idea that there are mechanisms at work (see also Teller 2010; Kuhlman and Glennan 2014).