The Republic: Books 2-3 
Socrates discusses the nature of a republic organized on rational lines:
   And shall we just carelessly allow children to hear any casual tales which may be devised by casual persons, and to receive into their minds ideas for the most part the very opposite of those which we should wish them to have when they are grown up? 
   We cannot. 
   Then the first thing will be to establish a censorship of the writers of fiction, and let the censors receive any tale of fiction which is good, and reject the bad; and we will desire mothers and nurses to tell their children the authorized ones only. Let them fashion the mind with such tales, even more fondly than they mould the body with their hands; but most of those which are now in use must be discarded....

   But which stories do you mean, he said; and what fault do you find with them? 
   A fault which is most serious, I said; the fault of telling a lie, and, what is more, a bad lie. 
   But when is this fault committed? 
   Whenever an erroneous representation is made of the nature of gods and heroes -- as when a painter paints a portrait not having the shadow of a likeness to the original. 

.... these tales must not be admitted into our State, whether they are supposed to have an allegorical meaning or not. For a young person cannot judge what is allegorical and what is literal; anything that he receives into his mind at that age is likely to become indelible and unalterable; and therefore it is most important 

....  poets and story-tellers are guilty of making the gravest misstatements when they tell us that wicked men are often happy, and the good miserable; and that injustice is profitable when undetected, but that justice is a man's own loss and another's gain -- these things we shall forbid them to utter, and command them to sing and say the opposite. 

..... And therefore when any one of these pantomimic gentlemen, who are so clever that they can imitate anything, comes to us, and makes a proposal to exhibit himself and his poetry, we will fall down and worship him as a sweet and holy and wonderful being; but we must also inform him that in our State such as he are not permitted to exist; the law will not allow them. And so when we have anointed him with myrrh, and set a garland of wool upon his head, we shall send him away to another city. For we mean to employ for our souls' health the rougher and severer poet or story-teller, who will imitate the style of the virtuous only, and will follow those models which we prescribed at first when we began the education of our soldiers.

....But shall our superintendence go no further, and are the poets only to be required by us to express the image of the good in their works, on pain, if they do anything else, of expulsion from our State? Or is the same control to be extended to other artists, and are they also to be prohibited from exhibiting the opposite forms of vice and intemperance and meanness and indecency in sculpture and building and the other creative arts; and is he who cannot conform to this rule of ours to be prevented from practising his art in our State, lest the taste of our citizens be corrupted by him? We would not have our guardians grow up amid images of moral deformity, as in some noxious pasture, and there browse and feed upon many a baneful herb and flower day by day, little by little, until they silently gather a festering mass of corruption in their own soul. Let our artists rather be those who are gifted to discern the true nature of the beautiful and graceful; then will our youth dwell in a land of health, amid fair sights and sounds, and receive the good in everything; and beauty, the effluence of fair works, shall flow into the eye and ear, like a health-giving breeze from a purer region, and insensibly draw the soul from earliest years into likeness and sympathy with the beauty of reason.