Demonstrates definitively that the secularization thesis is correct, and religion is losing its grip on societies worldwide In the decades since its introduction, secularization theory has been subjected to doubt and criticism from a number of leading scholars, who have variously claimed that it is wrong, flawed, or incomplete. In Beyond Doubt, Isabella Kasselstrand, Phil Zuckerman, and Ryan T. Cragun mount a strong defense for the theory, providing compelling evidence that religion is indeed declining globally as a result of modernization. Though defenses of secularization theory have been mounted in the past, we now have many years' worth of empirical data to illuminate trends, and can trace changes not just at a given point in time but over a trajectory. Drawing on extensive survey data from nations around the world, the book demonstrates that, in spite of its many detractors, there is robust empirical support for secularization theory. It also engages with the most prominent criticisms levied against the theory, showing that data that are said to refute the narrative of religious decline are easily explainable and in keeping with the broader tendency toward secularization. Beyond simply defending secularization theory, the authors endeavor to formalize it, offering clear definitions of relevant terms and creating propositions that can be repeatedly and accurately tested. Beyond Doubt offers the strongest argument to date for the existence of a global secularization trend, and will be a vital resource for students and scholars alike who study religion and secularism.