Since Aristotle’s theory of tragedy is thousands of years old, one may be tempted to think that it is no longer useful to us today in the same way that the geocentric model is no longer useful to us for describing the solar system. While this may be true of the geocentric model, it is not the case with Aristotle’s definition of tragedy. Even today we greatly enjoy the best Greek tragedies of the Classical Period (such as Oedipus Rex, The Persians, Antigone, Hecuba, The Trojan Women, Ajax, etc.), perhaps because they have something important to say about the human condition. However, most of the value-conferring features in these tragedies which we appreciate so much were described, discussed, and clarified in Aristotle’s theory. A knowledge of his theory will actually enable us to more fully comprehend the development and unfolding of the tragic plots. But the applicability of Aristotle’s theory is not confined to Greek tragedies. Shakespeare also employed many of the devices mentioned in the Poetics, and the awareness of important features described herein certainly helps our enjoyment of King Lear or even Macbeth. I will therefore focus on features (discussed in the Poetics) which are useful for enhancing our appreciation of Classical Greek tragedies and some of Shakespeare’s works. Most important of these features is the production of the tragic effect, which consists of two parts: (1) the arousal of pity and fear to their maximum and (2) the katharsis or purgation of these emotions. But the concept of katharsis has been interpreted in many ways, so this paper will attempt to seek the most appropriate interpretation of the concept. However, the maximisation of fear and pity leading to the katharsis of these emotions (the two processes of the tragic effect) can only be achieved by the unfolding of a well structured tragic plot, and the revelation of character qualities in the tragic play. The successful tragedies from Classical Greece and the Shakespearean era possess the plots that were structured in a manner so as to produce the tragic effect to its maximum. I will pay particular attention to Oedipus Rex of Sophocles and King Lear of Shakespeare to illustrate my point.