The title for MacLeish's poem, "Ars Poetica," comes from a treatise written sometime between 20 BC and 13 BC by Horace, a poet and critic. Originally titled Letters to Piso or Epistle to the Pisos, the Pisos being a prominent familial branch in Ancient Rome, it is now known as Ars Poetica, and seeks to outline the most important tenants of poetry and literature, much like Aristotle's Poetics. Among the principles Horace outlines are style, decorum, precision, sincerity, openness to critique, and knowledge.
Horace's work poem lays out nearly 30 principles, and spans 476 lines. Some examples of the dictums Horace includes in Ars Poetica are his assertion that per Greek tradition, traumatic events should not be performed on stage, but through narration, and that each genre of literature (epic poetry, tragedy etc.) must maintain its conventions.
Interestingly, though not translated into English until 1640, Ars Poetica has had an immense impact on literary culture, and many poets have written their own versions of the treatise, emphasizing what they feel are the most important tenants of the art of poetry. In this context, MacLeish's work is a clear rebellion against some of Horace's tenants, such as clarity of meaning, convention and precision. MacLeish's work also seems to take issue with the focus on rhetoric in early 20th century English poetry, for example. Since Horace's original poem, writers like MacLeish have been creating self-referential texts that grapple with how the literary arts should work.
