Not long after the witches have informed him that he will one day become king, Macbeth meditates upon his prophesied future and what might be necessary for him to bring that future into being. The thought that he could be required to become a regicide “[S]hakes so [his] single state of man, / That function is smother'd in surmise, / And nothing is, but what is not.” Shortly after considering that his coronation might occur without his taking any murderous action (“If Chance will have me King, why, Chance may crown me / Without my stir” [1. 3. 144–145]), Macbeth is interrupted in his musings, and he quickly apologizes for his preoccupation:

In the second half of this statement, Macbeth pledges that he will always remember the services performed for him by Angus, Rosse and Banquo; the register described here is the book of his memory, and Macbeth claims that he will daily turn its pages. However, he first tells us that he has been dwelling upon “things forgotten.”