 In other words, they argue that the conditions of the study can be seen to satisfy the conditions of the manipulability account, showing that drift ought to be understood as a (population-level) cause. Shapiro and Sober (2007) state that they endorse Reisman and Forber’s arguments as well as the view of drift as a process. However, it’s unclear whether Shapiro and Sober (or Reisman and Forber) actually do endorse the view of drift as a process. That is, it’s unclear why population size as a causal factor should count as a process.