The Preface to Aristotle's Art of Poetry

Dacier's insistence that the primary function of poetry is to instruct and that pleasure is merely an aid to that end could easily be distorted into a crudely moralistic view of the art. Doubtless it was this that recommended the treatise to minor critics and poets who were creating the atmosphere out of which came Jeremy Collier's attack on contemporary dramatists in 1698.
Samuel Holt Monk University of Minnesota

If I was to speak here of Aristotle 's Merit only, the excellence of his Poetick Art, and the reasons I had to publish it, I need do no more than refer the Reader to that Work, to shew the disorders into which the Theatre is long since fallen, and to let him see that as the Injustice of Men, gave occasion to the making of Laws; so the decay of Arts and the Faults committed in them, oblig'd first to the making Rules, and the renewing them. But in order to prevent the Objections of some, who scorn to be bound to any Rules, only that of their own fancy, I think it necessary, to prove, not only that Poetry is an Art, but that 'tis known and its Rules so certainly those which Aristotle gives us, that 'tis impossible to succeed any other way. This being prov'd, I shall examine the two Consequences which naturally flow from thence: First, that the Rules, and what pleases, are never contrary to one another, and that you can never obtain the latter without the former. Secondly, That Poesie being an Art can never be prejudicial to Mankind, and that 'twas invented and improv'd for their advantage only.
To follow this Method, 'tis necessary to trace Poetry from its Original, to shew that 'twas the Daughter of Religion, that at length 'twas vitiated, and debauch'd, and lastly, brought under the Rules of Art, which assisted, in Correcting the defaults of Nature.
God touch'd with Compassion for the Misery of Men, who were obliged to toil and labour, ordain'd Feasts to give them some rest; the offering of Sacrifices to himself, by way of Thanksgiving, for those Blessings they had received by his Bounty. This is a Truth which the Heathens themselves acknowledged; they not only imitated these Feasts, but spake of them as a Gift of the Gods, who having granted a time of Repose, requir'd some tokens of their grateful remembrance.