The central aim of this book is to make an argument, as persuasively as possible, for the concept of explanation—in all domains that human beings study—defended by Alfred North Whitehead. The authors believe, and passionately so, that the central insight of Whitehead’s philosophy has been passed over, misinterpreted, and forgotten even by his most sympathetic followers. The idea is both very simple and hard to keep in mind because it runs contrary both to our native habits of thinking and to our long-established ideas about what constitutes a satisfying explanation. Because its implications are far-reaching, subtle, disturbing, and complex, this approach to explanation has not taken hold, even among process philosophers. That must change.