conventicles of Christians meeting to study the Scriptures and devotional literature; the concept was first advanced in the 16th century by the German Protestant Reformer Martin Bucer (Bucer, Martin), an early associate of John Calvin (Calvin, John) in Strasbourg. Philipp Jakob Spener (Spener, Philipp Jakob) adopted the idea a century later in an effort to counteract what he perceived as the moral and spiritual indifference of the Protestant churches and to implement a program of reform that revolved around Bible study, devotional exercises, and personal piety. Spener had outlined this reform program in a book entitled Pia Desideria (“Pious Wishes”). This led to a religious revival in many German states and influenced not only the church but also society in general. Because of their emphasis on the practice of a pious life, Spener and his followers were called Pietists (Pietism).