This essay—a contribution to the Common Knowledge symposium on contextualism—is concerned with the gradual rise of awareness of the existence of modes of thought or systems of belief that are different from those that are dominant in one's own culture. The awareness can be found in the seventeenth and eighteenth centuries but was developed further in the early to mid-twentieth century. Its main consequence has been to encourage individuals to distance themselves from their own system—to criticize and change it.