 These metaphysical claims about drift (and selection and other evolutionary processes—but it is just drift that interests us here) set the stage for the statisticalists’ challenge. Matthen and Ariew (2002) challenge the claim that there is a defensible sense in which drift is a force. Aside from the fact that it does not have a predictable or constant direction (as Sober readily acknowledges), they point to a case of two similar populations subject to the same selective pressures, one in which the trait \(T\) becomes fixed and the other in which the alternative trait \(T'\) becomes fixed. What explains the outcome in the two cases? Exactly the same thing, Matthen and Ariew assert, just as exactly the same coin setup explains two heads and four heads in two series of ten coin tosses. Thus, they seem to suggest, there is no additional cause or force, “drift”. Walsh, Lewens, and Ariew (2002) similarly attack Sober’s claim that drift is a force; following Rosenberg (1994), they assert that “the events that are labelled ‘drift’ events, like lightning strikes, etc. are no different in kind from selection events” (Walsh, Lewens, and Ariew 2002: 457)—and thus, drift is not a distinct sort of force. Moreover, they argue, drift is best interpreted statistically as statistical error (see argument in  section 2.3),  and so again, it is not a force.