MACBETH: If it were done when 't is done, then 't were well
             It were done quickly. If the assassination
             Could trammel up the consequence, and catch,
             With his surcease, success; that but this blow
             Might be the be-all and the end-all -here,
             But here, upon this bank and shoal of time,
             We'd jump the life to come. But in these cases
             We still have judgement here, that we but teach
             Bloody instructions, which being taught return
             To plague th'inventor: This even-handed justice
             Commends th' ingredients of our poisoned chalice
             To our own lips. He's here in double trust:
             First, as I am his kinsman and his subject,
             Strong both against the deed; then, as his host,
             Who should against his murderer shut the door,
             Not bear the knife myself. Besides, this Duncan
             Hath borne his faculties so meek, hath been
             So clear in his great office, that his virtues
             Will plead like angels trumpet-tongued against
             The deep damnation of his taking-off,
             And pity, like a naked new-born babe,
             Striding the blast, or heaven's cherubin horsed
             Upon the sightless couriers of the air,
             Shall blow the horrid deed in every eye,
             That tears shall drown the wind. I have no spur
             To prick the sides of my intent, but only
             Vaulting ambition, which o'erleaps itself
             Inside the castle, Macbeth is 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 doom but realizes that even on earth, bloody actions "return To plague th'inventor" (I.vii.9–10). He then considers the reasons why he shouldn't kill Duncan: Macbeth is Duncan's kinsman, subject, and host; and the king is admired as a excellent ruler across the board. 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 k...