In his chapter “An Encounter with Radical Darwinitis” (2023), Raymond Tallis defines Darwinitis as “the claim that evolution completely explains the human person, and that the distinctive features of human beings are, or will be, best understood through the science of the evolved brain.” He argues that Darwinitis is false. I agree. I discuss the scope and limits of Darwin’s theory. I argue that a good scientific theory gives tools to explore its scope, and that a great scientific theory gives tools to determine its limits. Every scientific theory starts with assumptions. So every scientific theory has necessary limits.