Finally, tragedy is defined by its effect, the tragic catharsis. Tragedy “through pity and fear achieves its purgation of such emotions.”[24] It is complete, then, not only in action, but in emotion. Emotion is not merely aroused; it is satisfied; it is carried through to a release. Tragedy is thus thoroughly emotional, more emotional than any other form of art. It is emotional not incidentally, but essentially; for it offers not merely emotional excitement, but emotional satisfaction. As all art enhances by imitation our impressions of life, so tragedy reveals our motives and moves us onward through vicarious experience. We yearn toward our fellows moved as we are, only more deeply; we fear in some great crisis what obscurely threatens us all day by day; and we know the inevitable end not with our minds, but with our awakened hearts. From definition of tragedy by its essential characteristics Aristotle proceeds to enumeration of its constituents. Of these the _sine qua non_ is plot. The insistence on this is so ample and so convincing as hardly to need interpretation. Characterization comes second. Third is the expression of thought, as distinct from the expression of emotion or of character. The persons of the play not only reveal their individualities; they have also occasion to expound or persuade, and here poetic leans on rhetoric. For drama, though its movement is imaginative, though it primarily expresses emotion and character, cannot dispense with logic. Fourth is diction. Here again it is noteworthy that Aristotle puts this fourth, though tyros, he says, can master it before they can manage plot. Whether the diction be verse or prose he regards as negligible at this point. With the same brevity he enumerates finally musical and scenic accompaniments. What he enlarges upon is plot and characterization, and upon plot as the essential and determining factor. These distinctions made, let us thereupon discuss of what sort the plan of the actions (the plot) must be, since this is both the first and the greatest [constituent] of tragedy. We have shown tragedy to be imitation of an action complete and whole which has a certain magnitude. Though there is such a thing as a whole without any appreciable magnitude, we mean by a whole that which has beginning, middle, and end. A beginning is that which does not itself follow anything by causal necessity, but after which something else naturally is or comes to be. An end, on the contrary, is that which itself naturally follows some other thing, either by causal necessity or as a rule, but has nothing following it. A middle is that which follows something as some other thing follows it. Plots that are well planned, therefore, are such as do not begin or end at haphazard, but conform to the types just described.[25]