Chapter 7 maps out a broad framework for considering the problem of variation in evolution. Under the neo-Darwinian view that variation merely plays the role of supplying random infinitesimal raw materials, with no dispositional influence on the course of evolution, a substantive theory of form and its variation is not required to specify a complete theory of evolution. This view has been breaking down from the moment it was proposed, and is now seriously challenged by results from evo-devo, comparative genomics, molecular evolution, and quantitative genetics. For instance, the multivariate generalization of quantitative genetics indicates that selection cannot possibly act as an independent governing force. Replacing a theory of variation as fuel with a theory of variation as a dispositional factor will require, at minimum, an understanding of tendencies of variation (source laws), and an understanding of how those tendencies affect evolution (consequence laws).
An adaptive correlation ratio method
