The opening line of 1.4 provides an interesting scene juxtaposition–“Is execution done on Cawdor?” First, Macbeth spoke the last line of 1.3, and Duncan speaks this first of 1.4, neatly placing the two men/”rivals” side-by-side (it’s worth noting here that on Shakespeare’s stage the action was continuous; there would be no break, thus making the juxtapositioning even more significant). “Execution” ties in with the blood-laden imagery that permeates the play as a whole, and it also foreshadows Duncan’s murder/execution, not to mention Macbeth’s ultimate fate. Duncan is, of course, talking about the former Thane of Cawdor, but Macbeth is also the new Thane of Cawdor, and so there’s is some irony (given how events play out) in Duncan tying execution and Cawdor together, almost as a signel concept–had the new Thane been executed the play could have ended here and now!!!!!!!
The former Thane, notably, confessed his “treasons,” another shorthand method of raising issues of kingship and obedience that receive some emphasis in the second part of this scene. Irony again occurs when Duncan mentions he has “built an absolute trust” on the old Thane just at the moment that Macbeth arrives on stage and whom Duncan addresses as “worthiest cousin.” The greeting evokes another speech (from Macbeth) that delineates the relationships between monarch and subject: “The service and loyalty I owe, / In doing it pays itself. Your Highness’ part / Is to receive our duties, and our duties / Are to your throne and state children and servants, / Which do but what they should by doing everything / Safe toward your love and honor.” Again, in retrospect, the speech is grossly ironic.
Duncan’s announcement of Malcolm as his (natural) successor provokes an aside from Macbeth that reveals he is already thinking actively about fulfilling the Witches’ prophecies, rather than just letting events take their own course: “that is a step / On which I must fall down . . . Let not light see my black and deep desires.”