 To see even more starkly how what is called selection in the Price Equation differs from what is called selection in type recursions, consider a system exhibiting heterozygote superiority like the one from earlier, where \(w_{D} = w_{R} &lt; w_{H}.\) Recall that a system of this sort will evolve to a stable equilibrium (provided drift is idealized away). Using the recursive equations above, the reader can input values that meet the constraint that heterozygotes have the highest fitness, set \(p' = p,\) and compute the stable equilibrium value for \(p\), the frequency of the \(A\) alleles. If we understand selection as quantified by the fitness coefficients in this sort of set-up, then the whole time, selection operates in a constant fashion, since the fitness coefficients remain fixed. In particular, the operation of selection is the same when the system is evolving toward its stable equilibrium as when it remains at that stable equilibrium. By contrast, the covariance term in Price Equation model of the system will diminish in value until it reaches zero as the system evolves to its equilibrium state. When selection is identified with the covariance between type and reproduction, the frequency of the different types matters to the extent of selection. When selection is identified with fitness variables in type recursions, the frequency of different types has no influence on the extent of selection in the system. Thus, the different interpretations of selection that correspond to different quantities in different formal models are actually incompatible. We should expect, then, at least one of these interpretations of selection to fail, since focused selection cannot be two different things at once, at least if what counts as natural selection is non-arbitrary.