  The Price equation partitions total evolutionary change into two components.
The first component provides an abstract expression of natural selection. The
second component subsumes all other evolutionary processes, including changes
during transmission. The natural selection component is often used in
applications. Those applications attract widespread interest for their
simplicity of expression and ease of interpretation. Those same applications
attract widespread criticism by dropping the second component of evolutionary
change and by leaving unspecified the detailed assumptions needed for a
complete study of dynamics. Controversies over approximation and dynamics have
nothing to do with the Price equation itself, which is simply a mathematical
equivalence relation for total evolutionary change expressed in an alternative
form. Disagreements about approach have to do with the tension between the
relative valuation of abstract versus concrete analyses. The Price equation's
greatest value has been on the abstract side, particularly the invariance
relations that illuminate the understanding of natural selection. Those
abstract insights lay the foundation for applications in terms of kin
selection, information theory interpretations of natural selection, and
partitions of causes by path analysis. I discuss recent critiques of the Price
equation by Nowak and van Veelen.
