The writers studied here-Bodin, Montaigne, Locke, and Defoe-were instrumental in the historical and cultural changes that made an ethical norm of toleration more real. Because part of the reality they affected was ideational, we cannot explain it without examining the intricacies of their ideas. This does not mean that more concrete factors of interest, relations of power, economic structure, and other forces were not as, if not more, important. To explain as dramatic a change as the emergence of a fundamental modern value like toleration, one must acknowledge the ultimate power of what it is actually feasible to do-not just wish for. Yet, humans are creatures who use ideas to get things done, to imagine alternatives, and to move themselves and others to act, and therefore the languages and articulation of those ideas are causally significant. They are a cornerstone of that transformation.