I recently began reading Eric Havelock's Preface to Plato. What I have read so far concerns Plato's frontal and semi-frequent attack on dramatists and poets in Republic. His explanation for such an attack is primarily the effects that the medium of poetry has on its practitioners and audience, and the state of education in Greece as a result. The prevailing oral culture that existed up through Plato's time demanded some method of passing mores, norms, and all cultural knowledge onto the next generation. Havelock explains that this was primarily accomplished through the use of poetry and drama, which employed rhyming, meter, and what Plato describes as mimesis to impress this knowledge onto the audience. The first two characteristics are well-known; the third concerns a more abstract concept that Havelock takes a while to get to describing. In essence, mimesis is the imitation of reality that characterizes an actor's performance or a poet's change in voice to imitate character dialogue. Mimesis begins with the actor, poet, or rhapsodist and is transmitted to the audience so that the same imitation becomes a tool for remembrance. In short, it is hard to forget a memorable performance and the message that came along with it. For a society that lacked a widely-distributed writing system, such an effect was invaluable.
Plato's opposition to poetry requires some cultural context to make sense. In our largely written culture (despite the internet) poetry still serves largely as entertainment. This was not the case in Plato's time. As already described, it was considered a tool for education and entertainment, ubiqutious in many parts of life. This served the purpose of constant reinforcement of the poem's themes, which in them carried the Greek culture. As James Morrison Jr. wrote: "To an oral culture, triteness is inconceivable...". For something to be remembered and thus carried on, it must of course be memorable and impress itself on something more than just the memory of the word in isolation. It must be a theme observable in every day life, one that can be weaved with ease into any story, and incorporate any number of other things that would aid the memory of the lesson. Plato was disturbed with how these themes could be so easily and continually implanted into the minds of the common Greek who accepted them unquestionably. He understood that this was not the fault of the Greek, but a hallmark of the medium. For poetry to be effective at its task, objectivity must be abandoned. You could not simultaneously immerse yourself in a theme to remember and teach it while also questioning its nature and validity. This was the bane of Plato's philosophy, which hinged entirely on the belief that all could and should be rationally examined and explained. Because of this, he believed it had no place in education or entertainment, and was the primary opponent of philosophy.