 Jessica Pfeifer (2005) weighs in on the disagreement between Millstein and Brandon, arguing that it is reasonable to think that the source of probabilities in natural selection are at least partly a result of abstracting from or ignoring certain features of the environment and that, if this view is adopted, it is not conceptually confused to treat selection and drift as causally distinct. On Pfeifer’s view, drift is caused by the distribution of ignored factors, whereas selection for the trait in question is caused by those features that are not ignored.