 Here, the second term quantifies change due to drift (Okasha 2006: 33). Note how the \(\mu_{i}\) parameter quantifies deviation from expectation, and hence drift is a function of how the expectation is determined. Nothing about the Price Equation formalism constrains such determinations. In the warm/cold population, whether a given year’s evolution is quantified by the first right-hand side term, and hence constitutes change due to selection, or the second one, and hence constitutes change due to drift, will be determined by whether the theorist treats the weather as contributing to expected fitness. If, for instance, she is ignorant of how the weather changes year to year, she may treat the weather as drift; if she can predict it, she may not do so. Deployment of the Price Equation is compatible with both treating the weather as contributing to expected fitness and treating it as causing deviation from expectation.