"Sewall Wright was one of the principal authors of the Modern Synthesis, reconciling what in the early twentieth century were the antagonistic disciplines of evolution and genetics. Some of Wright's most unique contributions are epitomized in this volume. In particular, he elucidates why the proximate and ultimate consequences of gene action are not unique properties of individual genes themselves, but rather depend on the genetic and environmental context. The theoretical insights developed by Wright are foundational to studying the genetics of populations. They have been immensely influential in my own work and help unify approaches to understanding topics as seemingly disparate as the genetic basis of disease and the origin of new species."