Like many of Shakespeare's unhappier characters, Macbeth is, in some respects, an incompetent actor—he perishes, in a sense, because he chooses to live his life according to a script that he's underqualified to perform. With his reasonable, literal, dogged mind, he's ill-equipped to live in a world of son et lumière—he's quickly lost in the witches’ funhouse, in the realm of ambiguity conjured by his efforts to trace tangled chains of contingencies into the future. He is richly imaginative, but incapable of dissembling what he imagines. Again and again, Shakespeare emphasizes Macbeth's overtness, his inability to conceal himself, his sheer legibility to all the other characters: when Macbeth hears the witches prophesy his future glory, he is visibly startled—as Banquo says, “Good sir, why do you start, and seem to fear / Things that do sound so fair?” (1.3.51–52). Similarly, during the banquet scene, after Macbeth makes faces at an empty stool, he apologizes for his “strange infirmity” (3.4.85)—or as Lady Macbeth calls it, his “thing of custom” (3.4.96)—as if no one should think it strange that Macbeth is seized by weird fits of shouting at ghosts. Images in Macbeth's mind keep leaking out into the world around him and infecting his social behavior.

Macbeth is perfectly aware of his compulsive-expressive character, and sometimes gives himself advice in stage-acting: “False face must hide what the false heart doth know” (1.7.82), he remarks after deciding to murder Duncan; and, just before the banquet, he further reminds himself that, at all costs, he mustn’t let his subjects see his guilt inscribed on his face: the guilty pair must “make our faces vizards to our hearts, / Disguising what they are”—not easy when, as Macbeth admits, “full of scorpions is my mind” (3.2.34–35, 36). Yet Macbeth's histrionic efforts are largely in vain—he simply lacks the talent for acting. After the assassination, Macbeth does his best to seem shocked, shocked! by the discovery of the king's corpse, but he fools none of the more discerning spectators: Malcolm instantly turns to Donalbain and says, “To show an unfelt sorrow is an office / Which the false man does easy. I’ll to England” (2.3.136–37). When Macbeth feigns sorrow, he looks like a man feigning sorrow.