Seminal nineteenth-century thinkers predicted that religion would gradually fade in importance with the emergence of industrial society. The belief that religion was dying became the conventional wisdom in the social sciences during most of the twentieth century. The traditional secularization thesis needs updating, however, religion has not disappeared and is unlikely to do so. Nevertheless, the concept of secularization captures an important part of what is going on. This book develops a theory of existential security. It demonstrates that the publics of virtually all advanced industrial societies have been moving toward more secular orientations during the past half century, but also that the world as a whole now has more people with traditional religious views than ever before. This second edition expands the theory and provides new and updated evidence from a broad perspective and in a wide range of countries. This confirms that religiosity persists most strongly among vulnerable populations, especially in poorer nations and in failed states. Conversely, a systematic erosion of religious practices, values, and beliefs has occurred among the more prosperous strata in rich nations.