Aristotle proposes to approach poetry from a scientific viewpoint, examining the constituent parts of poetry and drawing conclusions from those observations. First, he lists the different kinds of poetry: epic poetry, tragedy, comedy, dithyrambic poetry, and most flute-playing and lyre-playing. Next, he remarks that all of these kinds of poetry are mimetic, or imitative, but that there are significant differences between them.
The first kind of distinction is the means they employ. Just as a painter employs paint and a sculptor employs stone, the poet employs language, rhythm, and harmony, either singly or in combinations. For instance, flute-playing and lyre-playing employ rhythm and harmony, while dance employs only rhythm. He also addresses the question of non-poetic language, arguing that poetry is essentially mimetic, whether it is in verse or in prose. Thus, Homer is a poet, while Empedocles, a philosopher who wrote in verse, is not. While Empedocles writes in verse, his writing is not mimetic, and so it is not poetry. In tragedy, comedy, and other kinds of poetry, rhythm, language, and harmony are all used. In some cases, as in lyric poetry, all three are used together, while in other cases, as in comedy or tragedy, the different parts come in to play at different times.
The second distinction is the objects that are imitated. All poetry represents actions with agents who are either better than us, worse than us, or quite like us. For instance, tragedy and epic poetry deal with characters who are better than us, while comedy and parody deal with characters who are worse than us.
The final distinction is with the manner of representation: the poet either speaks directly in narrative or assumes the characters of people in the narrative and speaks through them. For instance, many poets tell straight narratives while Homer alternates between narrative and accounts of speeches given by characters in his narrative. In tragedy and comedy, the poet speaks exclusively through assumed characters.
The very first paragraph of the Poetics gives us a hint as to how we should approach the work: it is meant to be descriptive rather than prescriptive. That is, Aristotle is not so much interested in arguing that poetry or tragedy should be one thing or another. Rather, he wants to look at past examples of poetry—tragedy in particular—and by dissecting them and examining their constituent parts to arrive at some general sense of what poetry is and how it works.
This is the same scientific method that Aristotle employs so successfully in examining natural phenomena: careful observation followed by tentative theories to explain the observations. The immediate and pressing question, then, is whether Aristotle is right in applying his scientific method to poetry. Physical phenomena are subject to unchanging, natural laws, and presumably a careful study of the phenomena matched with a little insight might uncover what these natural laws are. Aristotle seems to be proceeding with the assumption that the same is true for poetry: its growth and development has been guided by unchanging, natural laws, and the Poetics seeks to uncover these laws.
The results are mixed. In some cases, what Aristotle says seems quite right, while in others his conclusions seem very limiting. We will examine this question further when Aristotle delves deeper into the elements of tragedy.
Before going any further, we might do well to clarify some terms. When Aristotle talks about "art" or "poetry" he is not talking about what we might understand by these words. "Art" is the translation of the Greek word techne and is closely related to "artifice" and "artificial." Art for Aristotle is anything that is made by human beings as opposed to being found in nature. Thus, poetry, painting, and sculpture count as "art," but so do chairs, horseshoes, and sandals.
Our conception of "art" is more closely (but not exactly) approximated by what Aristotle calls "mimetic art." The Greek word mimesis defies exact translation, though "imitation" works quite well in the context of the Poetics. A chair is something you can sit in, but a painting of a chair is merely an imitation, or representation, of a real chair.
Paintings use paint to imitate real life, and sculptures use stone. Poetry is distinguished as the mimetic art that uses language, rhythm, and harmony to imitate real life, language obviously being the most crucial component.
This raises the question of in what way poetry imitates, or "mimics," real life. The events in Oedipus Rex did not actually happen in real life. In fact, it is important that tragedy be fictional and that there be an understanding that the events taking place on stage are not real: no one should call the police when Hamlet kills Polonius. Still, tragedy deals with humans who speak and act in a way that real humans conceivably could have spoken and acted. It is important that there be an understanding that the account is fictional, but it must also be close enough to reality that it is plausible.
There are significant differences between the kind of poetry discussed here and our conception of poetry. In modern times, the definition of poetry is closely linked to its being written in verse. Aristotle directly contradicts that definition, pointing out that Empedocles' philosophical verses are not poetry; they present ideas rather than imitate life.
Further, narrative is essential to Aristotle's definition of poetry. Not only comedy and tragedy, but also the epic poetry of the Greeks tells stories, as we find in the Iliad and the Odyssey. Both drama and epic poetry are fictional accounts that imitate real life in some way. On the other hand, a great deal of poetry in the modern world does not imitate life in any obvious way. For instance, the Robert Burns line, "My love is like a red, red rose" may be said to "imitate" or represent the poet's love for a woman, but by that token, Empedocles' verses might be said to "imitate" or represent certain philosophical concepts.
Aristotle is not trying to condemn Robert Burns for writing love poems; he is simply trying to catalog the different kinds of poetry that existed in his time. They all employ language, rhythm, and harmony in some way or another, they all deal with people who are engaging in certain kinds of action, and they all involve some sort of direct or indirect narrative. Whether something is an epic poem, a comedy, or a tragedy depends on how it fits within these categories. For instance, a tragedy is a composite of language, rhythm, and harmony that deals with agents who are on the whole better than us, and the poet speaks directly through these agents.