Every great tragedy is dominated by a protagonist who has within himself a tragic flaw, too much or too little of one of Aristotle's twelve virtues. In Macbeth, by William Shakespeare, Macbeth, a great Scottish general and thane of Glamis, has just won an important battle, when he is told by three witches that he will become thane of Cawdor and then king of Scotland. After Macbeth is given Cawdor by King Duncan, he takes the witches words for truth and conspires against Duncan with his wife. When Duncan comes to Macbeth's castle that night, Macbeth kills him and takes the crown for himself after Duncan's sons flee from Scotland. Then Macbeth reigns for a while, has several people killed, and is eventually slain by Macduff when he and Malcolm return leading the armies of England. Often people read the play and automatically conclude that Macbeth's tragic flaw is his ambition; that he is compelled to commit so many acts of violence by his lust for power. However, by carefully examining the first act, one can determine the defect in Macbeth's character that creates his ambition; his true tragic flaw. Macbeth's tragic flaw is not his ambition as most people believe, but rather his trust in the words of the witches and in his wife's decisions.
At the beginning of the play Macbeth has no designs on the throne, and he does not start plotting until his wife comes up with a plan. When first faced with the witches' words, Macbeth expresses astonishment and disbelief rather than welcoming them when he says, ".to be King stands not within the prospect of belief, no more than to be Cawdor."(1.3.73-75). When confronted with the witches' proclamation that he is to be king, Macbeth responds as a loyal subject would; not as a man with secret aspirations in his heart. He has no reason to hide his true feelings at this point so therefore it can be assumed that Macbeth has not yet truly considered killing the king.