On the surface, the plays seem to have nothing in common but witches. However, Macbeth and The Crucible are both about the perils of ambition. In Macbeth, the witches are (probably) real, but the ambition is the problem. The witches make a prophecy to Macbeth that he is going to be king, and he takes it and runs with it. Then, his desire to stay in control slowly destroys him and his kingdom. In The Crucible, there are no witches except the ones in Abigail’s head, and her ambition also slowly destroys Salem.
After hearing the witches make the prophecies, which are probably just to have a little fun with him, Macbeth decides that even though he is not named king, he is going to become king anyway. Then, after killing the former king Duncan, he is not done. He is worried that he can’t hold onto his ill-gotten gains without getting rid of other possible obstacles to his success, such as his supposed former friend Banquo, who also heard the prophecies.
To be thus is nothing;
But to be safely thus.--Our fears in Banquo
Stick deep; and in his royalty of nature
Reigns that which would be fear'd: 'tis much he dares;
And, to that dauntless temper of his mind,
He hath a wisdom that doth guide his valour
To act in safety. … (Act 3, Scene 1)
Macbeth sends murderers to kill Banquo, his son Fleance, and Macduff’s entire family. They fail to kill Macduff, who joins the heir to the throne, Malcolm, and comes for Macbeth with an army. The kingdom is torn by war for no reason, just because of Macbeth’s ambition and because some witches wanted to have some fun.
In some ways, Salem goes through similar chaos in The Crucible. It is also torn apart for no reason. Abigail Williams tries to make herself seem important and distract from her bad behavior. She also uses the witch trials as a way to get back at people she does not like, especially John Proctor for spurning her.
Most people seem to just go along with the witch trials, just as no one seems to have publicly questioned Macbeth. Hysteria gets the best of them. Proctor seems to be one of only a few who speaks against the witch trials.
PROCTOR: What work you do! It‘s strange work for a Christian girl to hang old women!
MARY: But, Mister Proctor, they will not hang them if they confess. Sarah Good will only sit in jail some time… and here‘s a wonder for you, think on this. Goody Good is pregnant! (Act II)
Although he spoke against them in his home, he was public too. When accused, Proctor also faced a choice. He could confess when he did nothing or be honest and go to his grave honest. For Proctor, doing the right thing in a sea of chaos was of the utmost importance.