Inside the castle, as oboes play and servants set a table for the evening's feast, Macbeth paces by himself, pondering his idea of assassinating Duncan. He says that the deed would be easy if he could be certain that it would not set in motion a series of terrible consequences. He declares his willingness to risk eternal damnation but realizes that even on earth, bloody actions "return / To plague th'inventor" (1.7.9–10). He then considers the reasons why he ought not to kill Duncan: Macbeth is Duncan's kinsman, subject, and host; moreover, the king is universally admired as a virtuous ruler. Macbeth notes that these circumstances offer him nothing that he can use to motivate himself. He faces the fact that there is no reason to kill the king other than his own ambition, which he realizes is an unreliable guide.
Lady Macbeth enters and tells her husband that the king has dined and that he has been asking for Macbeth. Macbeth declares that he no longer intends to kill Duncan. Lady Macbeth, outraged, calls him a coward and questions his manhood: "When you durst do it," she says, "then you were a man" (1.7.49). He asks her what will happen if they fail; she promises that as long as they are bold, they will be successful. Then she tells him her plan: while Duncan sleeps, she will give his chamberlains wine to make them drunk, and then she and Macbeth can slip in and murder Duncan. They will smear the blood of Duncan on the sleeping chamberlains to cast the guilt upon them. Astonished at the brilliance and daring of her plan, Macbeth tells his wife that her "undaunted mettle" makes him hope that she will only give birth to male children (1.7.73). He then agrees to proceed with the murder.
