Plato believed along with the Greek philosophers that poetry should be "well-ordered" and should attempt to "imitate the order" and harmony of nature. Plato was a Grrek philoosopher born 428-7 and died In 348-7 B.C.E.
Aristotle approach to literature is home formal and less morally. For aristotle this purpose is the evocation of fear and pity in the audience. He also thought that all poetry or literature should serve a purpose.