Aristotle points out that visualizing the action is crucial for a poet in order to avoid gaps in logic or inconsistencies. Rather than see the action in his head, Aristotle says the poet must work out the action 'before his eyes.'
Aristotle also suggests that a poet construct a general outline and then fill in episodes and detail. Thus, a poet can work out a play's essence, and then focus on the episodes that will support this essence and in effect, create 'unity.'
Every tragedy contains two parts - complication and unraveling (denouement). The complication refers to everything from the beginning of the action to the turning point, or climax where bad fortune turns to good, or good fortune turns to bad. The unraveling, or denouement, extends from the climax to the end, and tracks the final transformation of a hero to good or bad fortune.
Aristotle presents four kinds of tragedy:
a) complex - depending entirely on reversal and recognition at the climax
b) pathetic - motivated by passion
c) ethical - motivated by moral purpose
d) simple - without reversal or recognition
Aristotle concludes his discussion of reversal and recognition by suggesting that a tragedy should not assume an epic structure - involving many plots. One plot that creates unity of action is all that is required for tragic catharsis.
Aristotle moves on to diction next, or the expression of thought through speech. Speech can be divided into a) proof and refutation, b) excitation of feelings (pity, fear, and anger), or c) the suggestion of importance. Indeed, action can be divided similarly - but the difference between action and speech is that action can stand alone without exposition, while speech depends on the effect of the speech in order to gain a result. The speech, in itself, is an action.
Aristotle begins here with an important note on visualization. Whereas even many contemporary authors and instructors focus on the value of seeing the action 'in your head,' Aristotle points out that such methods inevitably lead to gaps in logic and inconsistencies, since the action is being conjured by an unreliable mind. Rather, the best way to determine whether the action of a given drama can sustain audience's interest and believability is by envisioning it 'before one's eyes' as if unfolding in a proscenium before the writer. As such, the writer becomes objective observer of the action and can immediately point out what does not follow from probable or necessary cause.
There are only two parts to a drama, says Aristotle - the complication and the denouement. More simply, the complication begins with an 'inciting incident,' a trigger that puts a chain of events in motion. At some point the chain reaches a climax, where the hero's fortunes must irreversibly turn from good to bad (a tragedy) or bad to good (a comedy). The denouement (or unraveling) is simply the end of this transformation that begins at the climax.
For instance, in Oedipus Rex, the complication sees us all the way through Oedipus discovering his own crimes - and from there, the denouement takes us through his self-mutilation and redemption. Often, then, the climax takes place at the moment of key reversal or recognition in a tragedy. Without this reversal or recognition, the author must rely on some other form of invention in order to create a climax - either 'ethics' or 'passion' as Aristotle states in his summary of the types of tragedy, or a purposeful 'simplicity' to the drama.
Aristotle's definition of 'diction' is revelatory even in contemporary academic circles, because it subjugates speech to action without condition. For Aristotle, action is always paramount - even without speech at all, one could create a perfectly sustainable, even masterful drama. Speech, then, must be seen as an action in itself and not a complement to action.
Indeed, the best speech has the same purpose as action - to either prove or refute, incite fear or pity, or suggest significance. The last is where speech might prove more useful than physical action in most cases - since the highlighting of a particular object or character can be done more simply with words than with the limitations of staging. That said, one can also point to film as a genre where suggesting significance is nearly always done without words - the shot of the gun in the drawer, for instance, nearly always tells us that the gun will reappear at the climax of the film. Ultimately, then, speech must simply do what action can accomplish with less effort - which is to direct the audience's attention to a given purpose, emotion, or significance.