Because the title of this article is ambiguous, I will begin by sharpening the issue of the justification of prayer. The point, in the first place, is to see how Calvin and Barth, as Reformed theologians, answer the question, “Why pray?” A second interest emerges in the discussion: prayer provides a case for illustrating the significant differences in the reasoning of Calvin and Barth on matters of ethics. In particular, the case of prayer indicates the way that Calvin's ruledeontology allows an important (albeit circumscribed) role for teleological appeals in the justification of prayer. Barth's act-deonotological theory consistently eschews such appeals. And this fact leads to a third interest of the paper: what are the strengths and weaknesses of the Reformed tradition for discussions of “spirituality” and ethics? If “spirituality” entails, as some would argue, a notion of “spiritual exercises” aimed at the cultivation of certain dispositions/virtues requisite to the vision of God, can Reformed theology have a “spirituality”? I argue that it can, but only if it is possible to preserve the teleological dimensions of Calvin's justification for acts such as prayer, which (as he would have it) is the “chief exercise of faith.”