 In a recent paper, Walsh, Ariew, and Matthen put forward a case of temporally variable selection and claim that it could be treated as a case either of selection or of drift (2017). The case is of a discrete-generation system with yearly reproduction in which each of two types of organisms produce different numbers of offspring depending on whether the year is warm or cold, with each type of year being equally probable: the H types produce 6 offspring in warm years while the T types produce 4, and the reverse holds for cold years. The authors take the position that the system “looks like” both a case of selection and a case of drift, but without consideration of any formal model of it. Instead, we are invited to think it is a case of selection because the fitnesses of the different types vary year-to-year; we are invited to think it is a case of drift because, allegedly, over long stretches of time the two types have equal fitnesses and we should, allegedly, predict no net increase in frequency for either type (Walsh, Ariew, &amp; Matthen 2017: 12–13).