Aristotle proposes to study poetry by analyzing its constitutive parts and then drawing general conclusions. The portion of the Poetics that survives discusses mainly tragedy and epic poetry. We know that Aristotle also wrote a treatise on comedy that has been lost. He defines poetry as the mimetic, or imitative, use of language, rhythm, and harmony, separately or in combination. Poetry is mimetic in that it creates a representation of objects and events in the world, unlike philosophy, for example, which presents ideas. Humans are naturally drawn to imitation, and so poetry has a strong pull on us. It can also be an excellent learning device, since we can coolly observe imitations of things like dead bodies and disgusting animals when the real thing would disturb us.

Aristotle identifies tragedy as the most refined version of poetry dealing with lofty matters and comedy as the most refined version of poetry dealing with base matters. He traces a brief and speculative history of tragedy as it evolved from dithyrambic hymns in praise of the god Dionysus. Dithyrambs were sung by a large choir, sometimes featuring a narrator. Aeschylus invented tragedy by bringing a second actor into dialogue with the narrator. Sophocles innovated further by introducing a third actor, and gradually tragedy shifted to its contemporary dramatic form.

Aristotle defines tragedy according to seven characteristics: (1) it is mimetic, (2) it is serious, (3) it tells a full story of an appropriate length, (4) it contains rhythm and harmony, (5) rhythm and harmony occur in different combinations in different parts of the tragedy, (6) it is performed rather than narrated, and (7) it arouses feelings of pity and fear and then purges these feelings through catharsis. A tragedy consists of six component parts, which are listed here in order from most important to least important: plot, character, thought, diction, melody, and spectacle.

A well-formed plot must have a beginning, which is not a necessary consequence of any previous action; a middle, which follows logically from the beginning; and an end, which follows logically from the middle and from which no further action necessarily follows. The plot should be unified, meaning that every element of the plot should tie in to the rest of the plot, leaving no loose ends. This kind of unity allows tragedy to express universal themes powerfully, which makes it superior to history, which can only talk about particular events. Episodic plots are bad because there is no necessity to the sequence of events. The best kind of plot contains surprises, but surprises that, in retrospect, fit logically into the sequence of events. The best kinds of surprises are brought about by peripeteia, or reversal of fortune, and anagnorisis, or discovery. A good plot progresses like a knot that is tied up with increasingly greater complexity until the moment of peripeteia, at which point the knot is gradually untied until it reaches a completely unknotted conclusion.

For a tragedy to arouse pity and fear, we must observe a hero who is relatively noble going from happiness to misery as a result of error on the part of the hero. Our pity and fear is aroused most when it is family members who harm one another rather than enemies or strangers. In the best kind of plot, one character narrowly avoids killing a family member unwittingly thanks to an anagnorisis that reveals the family connection. The hero must have good qualities appropriate to his or her station and should be portrayed realistically and consistently. Since both the character of the hero and the plot must have logical consistency, Aristotle concludes that the untying of the plot must follow as a necessary consequence of the plot and not from stage artifice, like a deus ex machina (a machine used in some plays, in which an actor playing one of the gods was lowered onto the stage at the end).

Aristotle discusses thought and diction and then moves on to address epic poetry. Whereas tragedy consists of actions presented in a dramatic form, epic poetry consists of verse presented in a narrative form. Tragedy and epic poetry have many common qualities, most notably the unity of plot and similar subject matter. However, epic poetry can be longer than tragedy, and because it is not performed, it can deal with more fantastic action with a much wider scope. By contrast, tragedy can be more focused and takes advantage of the devices of music and spectacle. Epic poetry and tragedy are also written in different meters. After defending poetry against charges that it deals with improbable or impossible events, Aristotle concludes by weighing tragedy against epic poetry and determining that tragedy is on the whole superior.

Aristotle takes a scientific approach to poetry, which bears as many disadvantages as advantages. He studies poetry as he would a natural phenomenon, observing and analyzing first, and only afterward making tentative hypotheses and recommendations. The scientific approach works best at identifying the objective, lawlike behavior that underlies the phenomena being observed. To this end, Aristotle draws some important general conclusions about the nature of poetry and how it achieves its effects. However, in assuming that there are objective laws underlying poetry, Aristotle fails to appreciate the ways in which art often progresses precisely by overturning the assumed laws of a previous generation. If every play were written in strict accordance with a given set of laws for a long enough time, a revolutionary playwright would be able to achieve powerful effects by consciously violating these laws. In point of fact, Euripides, the last of the three great tragic poets of Ancient Greece, wrote many plays that violated the logical and structured principles of Aristotle’s Poetics in a conscious effort to depict a world that he saw as neither logical nor structured. Aristotle himself gives mixed reviews to Euripides’ troubling plays, but they are still performed two and a half millennia after they were written.

Aristotle’s concept of mimesis helps him to explain what is distinctive about our experience of art. Poetry is mimetic, meaning that it invites us to imagine its subject matter as real while acknowledging that it is in fact fictional. When Aristotle contrasts poetry with philosophy, his point is not so much that poetry is mimetic because it portrays what is real while philosophy is nonmimetic because it portrays only ideas. Rather, the point is that the ideas discussed in philosophical texts are as real as any ideas ever are. When we see an actor playing Oedipus, this actor is clearly a substitute through which we can imagine what a real Oedipus might be like. When we read Aristotle’s ideas on art, we are in direct contact with the ideas, and there is nothing more real to imagine. Art presents reality at one level of remove, allowing us a certain detachment. We do not call the police when we see Hamlet kill Polonius because we know that we are not seeing a real event but only two actors imitating real-world possibilities. Because we are conscious of the mimesis involved in art, we are detached enough that we can reflect on what we are experiencing and so learn from it. Witnessing a murder in real life is emotionally scarring. Witnessing a murder on stage gives us a chance to reflect on the nature and causes of human violence so that we can lead a more reflective and sensitive life.

Aristotle identifies catharsis as the distinctive experience of art, though it is not clear whether he means that catharsis is the purpose of art or simply an effect. The Greek word katharsis originally means purging or purification and refers also to the induction of vomiting by a doctor to rid the body of impurities. Aristotle uses the term metaphorically to refer to the release of the emotions of pity and fear built up in a dramatic performance. Because dramatic performances end, whereas life goes on, we can let go of the tension that builds during a dramatic performance in a way that we often cannot let go of the tension that builds up over the course of our lives. Because we can let go of it, the emotional intensity of art deepens us, whereas emotional intensity in life often just hardens us. However, if this process of catharsis that allows us to experience powerful emotions and then let them go is the ultimate purpose of art, then art becomes the equivalent of therapy. If we define catharsis as the purpose of art, we have failed to define art in a way that explains why it is still necessary in an era of psychiatry. A more generous reading of Aristotle might interpret catharsis as a means to a less easily defined end, which involves a deeper capacity for feeling and compassion, a deeper awareness of what our humanity consists in.

Aristotle insists on the primacy of plot because the plot is ultimately what we can learn from in a piece of art. The word we translate as “plot” is the Greek word muthos, which is the root for myth. Muthos is a more general term than plot, as it can apply to any art form, including music or sculpture. The muthos of a piece of art is its general structure and organization, the form according to which the themes and ideas in the piece of art make themselves apparent. The plot of a story, as the term is used in the Poetics, is not the sequence of events so much as the logical relationships that exist between events. For Aristotle, the tighter the logical relationships between events, the better the plot. Oedipus Rex is a powerful tragedy precisely because we can see the logical inevitability with which the events in the story fall together. The logical relationships between events in a story help us to perceive logical relationships between the events in our own lives. In essence, tragedy shows us patterns in human experience that we can then use to make sense of our own experience.