This chapter presents the theology of John Calvin, whose Reformed Theology is the basis of Presbyterian denominational beliefs, as it addresses mystical religious experience. A clear distinction is given between his full theology, which embraces both the intellectual and experiential aspects of faith, and Calvinism, a truncated version of his theology that ignores the experiential aspect of faith. The theology of Jonathan Edwards, a Reformed theologian in eighteenth-century America, is also presented, as it expresses Calvin’s theology of mystical experience in the face of the Great Awakening that originated with Edwards’ congregation. Edwards’ method of distinguishing authentic from inauthentic religious experience is discussed.