This is not a theological trestise on the one hand, nor on the other is it a volume of sermons. Like its predecessor, the volume on Prayer, it has a distinct office to fulfill, an office that in the judgment of the editor is of immense importance. For between and the professor's lecture-room and the preacher's study there is a great gulf fixed. In the lecture-room the lectures on systematic theology are laboriously entered into notebooks, which are useful for the exit examinations. But when the active work of the ministry begins and so many sermons have to be prepared every week, the cupboard into which those notebooks have been stowed away is left undisturbed. The preacher begins to spin his sermons out of his own brains, with the assistance of such popular books as happen to be at his hand. -- From the Preface