"The most important element is the construction of the plot. Tragedy is a representation not of persons but of action and life, and happiness and unhappiness consist in action." (1450a, 15ff)
"What is poetry, how many kinds of it are there, and what are their specific effects?" These are questions that Aristotle’s Poetics, one of his most influential books, attempts to answer. While it has been an important aspect outside philosophical circles it is doubtful that it can be fully appreciated outside Aristotle’s philosophical system as a whole.
A theme common to all Aristotle’s philosophy is the claim that nothing can be understood apart from its end or purpose (telos). This is certainly true for the Poetics which seeks to discover the end or purpose of all the poetic arts, and especially of tragic drama. Aristotle argues that generally, the goal of poetry is to provide pleasure of a particular kind. For comparison the Metaphysics begins, “All men desire to know by nature,” and the Nicomachean Ethics repeatedly says that the satisfaction of natural desires is the greatest source of lasting pleasure. The Poetics combines these two approaches with the idea of imitation. All people by nature enjoy a good imitation (that is, a picture or drama) because they enjoy learning, and imitations help them to learn.
Of particular interest to Aristotle is the pleasure derived from tragic drama, namely, the kind of pleasure that comes from the purging or cleansing (catharsis) of the emotions of fear and pity. Though the emotions of fear and pity are not to be completely eliminated, excessive amounts of these emotions are not characteristic of a flourishing individual. Vicariously experiencing fear and pity in a good tragedy cleanses the soul of ill humors.
Though there are many elements of a good tragedy, the most important, according to Aristotle, is the plot. The centrality of plot once again follows from central doctrines of the Metaphysics and the Nichomachean Ethics. In the former, Aristotle argues that all knowledge is knowledge of universals; in the latter, he states that it is through their own proper activity that humans discover fulfillment.
For a plot to work, it must be both complete and coherent. That means that it must constitute a whole with a beginning, middle, and end, and that the sequence of events must exhibit some sort of necessity. A good dramatic plot is unlike history. History has no beginning, middle, and end, and thus it lacks completeness. Furthermore, it lacks coherence because many events in history happen by accident. In a good dramatic plot, however, everything happens for a reason. This difference makes tragedy philosophically more interesting than history. Tragedy focuses on universal causes and effects and thus provides a kind of knowledge that history, which largely comprises accidental happenings, cannot.
While literary styles have changed over the centuries, the observations of Aristotle still contain value both for writers and readers today.