In Poetics, Aristotle says that a typical tragedy is formed of these six components: Plot,Character,Thought,Diction,Spectacle and Song. He further says: 'Plot is the most important, since tragedy is a representation not of men but of action and life...there could be no tragedy without action but there could be oe without character.' Thus, we can understand that according to Aristotle, plot is responsible for arousing the emotions of love,pity and fear-through incidents in a damatic form and not in narrative form.He further mentions that the action of a tragic plot must have a beginning,a middle and an end. All parts are equally essential to the whole,i.e., the plot,and so they must be properly ordered with an appreciable coherence.
He distinguishes two types of plots: Simple and Complex. Simple plot is one in which change of fortune takes place without reversal or 'Perpeteia',while a complex plot is one where the cahnge of fortune is accompanied by a reversal or recognition or discovery or both 'Perpeteia' and 'Anagnorisis', i.e., 'change from ignorance to knowledge.'
Here we see that ,Plot is closely related to Aristotle's concept of 'Hamartia-an error of judgement'and 'Katharsis-purgation or purification of soul of all its excessive emotions.' So, to depict the 'Hamartia' in an effective and efficient way to bring about an effective and proper 'Katharsis',plot has to be very cleary and appropriately integrated to depict the actions of men and life. Hence, I feel this is the reason why plot is so important according to Aristotle.