The pious layman Robert Nelson's 1704 tract A Companion for the Festivals and Fasts of the Church of England was arguably the most popular and important Anglican devotional work of the eighteenth century. Ostensibly a simple guidebook to the Anglican liturgical calendar, Nelson's Festivals and Fasts was, in fact, a précis of Anglican theology and ecclesiology. What has been less clearly recognized, however, was the extent to which Nelson's Festivals and Fasts was also a sharply polemical work. This article considers Nelson's tract as a defense of “the sacred” as demarcating a socially and cognitively distinct sphere of life. Nelson's work takes great pains to maintain the spaces, offices, festivals and personnel of the church as “set apart” from the commerce of everyday life; and nearly every page exudes a fear of encroachment on the sacred. Nelson's conception of the sacred, and the manifold threats to its differentiation, provokes a reconsideration of the prevalent narratives of religious transformation in the early English enlightenment. Most importantly, it underscores the serious limitations of the current debate over secularization in this period.