In this essay Derrida reflects, for the first time at length, on secularization as a historical process. Whereas his earlier writings on religion focus on Jewish and Christian authors who blur the boundaries of religious belonging, this essay directly questions the categories of religion and secularization. Against this background, Derrida revisits the work of Kant, Voltaire, Nietzsche, and Heidegger, and he reflects on his own engagement with messianism, negative theology, and the khôra.