What, then, are the statisticalist issues that random drift is entangled with? The concerns raised by Walsh, Lewens, and Ariew (2002) and Matthen and Ariew (2002) have their origins in claims made by Sober (1984) in his classic The Nature of Selection. Sober characterizes evolutionary theory as a theory of forces, with its zero-force state described by the Hardy-Weinberg equation of population genetics (see the population genetics entry for an explanation of the equation); in such a state, the