According to Aristotle, a tragedy by definition is a drama or literary work in which the main character, a "tragic hero", is brought to ruin through process of reversal, especially as a consequence of a tragic flaw, yet also achieving a degree of truth throughout the downfall through the process of recognition. Shakespeare's Macbeth is considered by some to be a tragedy, but in actuality fails to fit the majority of the points necessary to be a tragedy. .
In examining the "tragic hero", Macbeth, Aristotle states that the character must be suitable to the situation, believable by the audience and consistent in his behavior. Macbeth fails to meet this requirement of a "tragic hero" mainly because he is not believable by the audience. It is clear that he has a conscience because of the struggle that takes place within him regarding whether or not he should agree to Lady Macbeth's plan to kill the king. This is evident when Macbeth dismissed the idea by saying, "We will proceed no further in this business". This is also clear later in the scene after Lady Macbeth questions whether he is a real man, when he replies, "Prithee, peace: I dare do all that may become a man; who dares do more is none". Even with his obvious presence of a conscience he still kills the king. After he commits the murder, Macbeth shows regret and remorse for his recent actions. This is clear when he says, "Still it cried "Sleep no more!" to all the house: "Glamis hath murder"d sleep, and therefore Cawdor shall sleep no more: Macbeth shall sleep no more". Even after feeling great remorse and doubt Macbeth continues to kill and seems to lose his conscience. This makes his character somewhat unbelievable because Macbeth demonstrates such strong doubt and regret, which strangely seems not to influence his actions just moments after expressing his mind-set. It is unbelievable that a purely evil character can posses and express any sort of conscience.
