Inside the castle, as oboes play and servants set a table for the evening’s feast, Macbeth paces by himself, pondering his idea of asassinating 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 wilingness to risk eternal damnation but realizes that even on earth, bloody actions “return To plague th’inventor”. He then considers the reasons why he should not kill Duncan, Macbeth is Duncan’s kinsman, subject, and host, moreover, the king is universally admired as a virtuous ruler. Macbeth notes that these circemstances 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.