Act 4, Scene 1: the second prophecy

The witches seem to prepare another spell to trick Macbeth

In Act 4, Scene 1, Macbeth seeks out the three witches to get some answers to what troubles him about their original prophecy, which was delivered in Act 1, Scene 3. However, before Macbeth enters the stage, we see the witches engaged in a very witch-like activity: They chant and dance around a bubbling cauldron while throwing scary and disgusting ingredients into it, such as the “Finger of [a] birth-strangled babe” (4.1.30). The witches then conclude that “the charm is firm and good” (4.1.38). Afterwards, the unsuspecting Macbeth enters. 

All of this indicates that the witches have prepared a spell to trick Macbeth, just like they did in Act 1, Scene 3. There is no doubt that Macbeth’s own lust for power spurs him on, but we could also interpret the witches’ spell as a sign that he is being manipulated or enchanted. This would take away some of the responsibility for his cruel actions. Also note how the presence of thunder underlines the danger associated with the witches.

The fact that Macbeth does not see the witches prepare...