In Rhetoric imagination is present for the sake of passion (and, therefore, in the long run, for the sake of action), while in poetry passion is present for the sake of imagination, and therefore, in the long run, for the sake of wisdom or spiritual health--the rightness and richness of a man's total response to the world. Such rightness, of course, has a tendency to contribute indirectly to right action, besides being in itself exhilarating and tranquillizing; that is why the old critics were right enough when they said that Poetry taught by delighting, or delighted by teaching. . . . Poetry certainly aims at making the reader's mind what it was not before. The idea of a poetry which exists only for the poet -- a poetry which the public rather overhears than hears--is a foolish novelty . . . There is nothing specially admirable in talking to oneself. Indeed, it is arguable that Himself is the very audience before whom a man postures most and on whom he practices the most elaborate deceptions.

C. S. Lewis, A Preface to Paradise Lost, p. 54