Here's a paragraph from the conclusion of Olson's "An Outline of Poetic Theory":
"Thus far we have proceeded on the supposition that the imitative poetic arts have as their ends certain pleasures, produced through their play upon our emotions. Certainly, these are ends of art and such as any consideration of art must embrace; but to suppose that art has no further effect and that it may have no further ends relative to these is vastly to underestimate the powers of art. It exercises, for example, a compelling influence upon human action - individual, social, or political - for among the causes of the misdirection of human action are the failure to conceive vividly and the failure to conceive apart from self-interest; and these are failures which art above all other things is potent to avert, since it vivifies, and since in art we must view man on his merits and not in relation to our private interests. It is not that art teaches by precept, as older generations thought, not that it moves to action; but clearly it inculcates moral attitudes; it determines our feelings toward characters of a certain kind for no other reason than that they are such characters. The ethical function of art, therefore, is never in opposition to the purely artistic end; on the contrary, it is best achieved when the artistic end is best accomplished, for it is only a further consequence of the powers of art. The same is true of any political or social ends of art, provided that the state be a good state or the society a moral society. To reflect on these things is to realize the importance and value of art, which, excellent in itself, becomes ever more excellent as we view it in ever more general relations."