What is poetic justice, and how far is it found in Macbeth by William Shakespeare?
[The complexity of the topic and space limit the extent of the application of the concept to a broad coverage of Macbeth.] Poetic justice is a very interesting, as well as an ancient concept evidenced as far back as Roman poet Horace and Greek essayist Plutarch. The concept was given the definitive phrase "poetic justice" in 1678 by Thomas Rymer in his critique of sixteenth century drama The Tragedies of the Last Age Considere'd.
Poetic justice has two parts to it and, until the period of Restoration comedy, was considered a requisite for all drama. Essayist and poet, Sir Philip Sidney, stated in Defense of Poetry that the presence of poetic justice was the only justification for fiction in a civilized society: fiction without poetic justice should be rejected and not written.
The two parts of poetic justice are (1) moral end results and (2) logical progression and results. Moral end results is my term for the need in dramatic works to have morally good and virtuous characters be rewarded, while the characters demonstrating vice must be punished. Said in standard form, the literary device of poetic justice requires virtue ultimately be rewarded and vice ultimately be punished. Logical progression and end results is my term for the requirement in dramatic works that the action and characters progress according to logic and that the end result be the logical outcome of the preceding action and characterization.
As an example of the above, using another work by Shakespeare, King Lear may be criticized as not following logically because, though the actions follow an acceptable logic, Lear's transformations, according to some critics, are not logical. In other words, an intuitively blind individual cannot become a perceptive individual in the course of a dramatic work (although a rebuttal might be that this principle does not seem to be at work in Aristotle's poetics, i.e., regarding Oedipus Rex). To put this part of poetic justice in more standard terms, the literary device of poetic justice also requires the triumph of the limits of logic. In other words, critics would deny that the events happening to Lear would be enough for him to have a transformation; thusly, this eliminates epiphany and revelation from the purview of logic in drama.
Now, to apply this to the two central characters in Macbeth. Critics might say that Macbeth's transformation from a noble warrior and leader into a grasping pawn of (someone else's) ambition does not follow logic: characters do not logically change qualities in mid action. Proponents of Shakespeare's aesthetic might say that the dual catalysts of (1) scary prophetic witches who follow directly after battle, victory, and reward, and (2) a demanding, insulting power-crazed wife might be quite enough to shock a man into a digression from virtue to vice. Thus, critics of Shakespeare might say poetic justice does not apply to Macbeth, even though after Macbeth does turn to vice, his vice is punished. Regarding Lady Macbeth, critics and proponents might both agree that poetic justice is present in logic, as she does not have any epiphany or revelation spurred character changes: she is corrupt: she stays corrupt. Both might also agree that in Lady Macbeth vice is punished, first by her guilt-tortured madness and later by the loss of everything she possesses, including Macbeth himself. Thus, both might say poetic justice does indeed apply to Lady Macbeth.