 One way to reconcile these competing interpretations of selection is to make first right-hand side term in the Price Equation quantify the extent of the influence of selection in a system. If we assume that focused selection accounts for whatever covariance exists between parental offspring number and phenotype, then we may treat the first right-hand side term of the Price Equation as a measure of the extent of the influence of focused selection, at least at a given type frequency (see Okasha 2006: 26). This approach puts the logical house in order, allowing for a univocal concept of selection, but it does so at the expense of other commitments. To note just one, the Price Equation will no longer be causally interpretable, since its quantities may no longer be said to represent causes (but instead measure the extents of their influences given further limiting assumptions). There exists a sizable literature on which of multiple alternative manipulations of the Price Equation represents the actual causal structure of different sorts of system (see Okasha 2016 and  section 5  below for more on this issue).