This little volume does not profess to be an exhaustive discussion of a subject which has so many sides, as this of prayer. But so far as known to the author, there is no book which collects and refutes the various objections urged by different classes of sceptics. Nor is there to be found anywhere a full articulation of prayer in the system of grace. There seemed to be a gap here which ought to be filled, which is all that this essay attempts. - Introductory note.