 Recently, Simpson’s Paradox has been invoked in an ongoing debate regarding whether natural selection should be understood as causal or statistical. Walsh (2010), a prominent defender of the statistical view, points to cases of Simpson’s Paradox as showing that selection cannot be understood causally, and Otsuka, Turner, Allen, &amp; Lloyd (2011) rebut this claim. An important point that emerges from this debate is that the term “population” is used differently in discussions of Simpson’s Paradox than it is in biology (cf. Weinberger 2018). Walsh presents an example in which a correlation in a population disappears when one splits the population into two parts. As Otsuka et al. point out, within population genetics, population size can be causally relevant to the fitness of its individuals. Note that Walsh’s example of dividing a population in half is not what we have been talking about in the context of Simpson’s Paradox. In the prior discussion, dividing the population was not a matter of changing its size, but rather of partitioning its probability distribution based on a variable.