This is not bravado trying to steady itself in a breeze of horror.
In order to break Macbeth down, and fully identify him with the deed of which Banquo was the horrible shadow, his temperament required that the ghost should vanish and reappear at the moment when he recovers composure. Shakspeare has marked, by Macbeth's sudden change of demeanor, that he was usually familiar with these coinages of his brain. To whatever ecstasy his feeling rose, with or without his wife's complicity, Shakspeare would have us understand that Macbeth was so fluent with these bodiless creations that he had naturalized the night-side of his mind. Therefore, Banquo must re-enter precisely when Macbeth drinks to the general joy, and to the dead man in particular. Shakspeare knew the moment when to spill Macbeth's wine and all his hardihood by putting out a disembodied hand to strike the goblet from his grasp. It was the very nick of time, but it was in the man's own temper.
Let us see how it was. The alteration of demeanor from astonishment to the abjectness of a guilty terror slips out of Macbeth's conviviality into the company, as he calls for wine and drinks "love and health to all." At the rim of his goblet he can even banter with his consciousness of murder: he is in a frame to enjoy proposing the health of
"Our dear friend, Banquo, whom we miss;
Would he were here!"
Now this pretence of desiring Banquo's presence uses up what resistance Macbeth has to spare. No sooner are the words out of his mouth than he imagines how they might be answered: the imagining it is the vivid answer. When you try jauntily to job off suspicion before other persons, the cheek grows pale with dread of being contradicted. A door is thrown ajar by this wind of pretending that nothing has been committed. Come on, there! the villain cries. Has any thing happened? Is anybody outside? Let him enter and take a look around! Sure enough, 'tis there: his mind's eye sees it enter. Even when the small faults of social life are denied or disclaimed by us, a ghost is raised upon the face, a dubious semblance of your guilt in the evasive eye, or just a flicker in the corner of the mouth. Most people overestimate their strength to make a flat denial of misdeeds when their soul is reflected in the polished mirrors of watchful eyes. There is a non-committal look which collars a man, puts him in the dock, and sends him to jail before he knows that he has been apprehended.
Prosaic men with no imagination to defy can preserve a smug complacency after the commission of a crime, because they cannot vibrate to it. Give a stroke to their thick temper, and it only answers with a thud. Their face is an emotionless Sahara, over which no showery gusts or smiles of April linger. But Macbeth was delicately strung: the slightest stir of the invisible air was registered by a vibration. When the ghost slips out of his own phrase, 'twas too pat,—this coming at the toast, "to the general joy of the whole table," at this pretence of thirst to drink a dead man's welfare; too nicely timed for flesh and blood to bear; too suggestive of continual liability to see the eyes glaring across the brim of any moment. Observing how easily the awful figure can thicken out of invisibility, he cries, "Take any shape but that!" And his mind is desperate to exorcise it into an "unreal mockery," and vainly struggles with his own personifying power.
"It will have blood; they say, blood will have blood."
It is a cold, calculating vengeance, marrowless, bloodless, but alert in a shape against which Macbeth's nerves at any time may stumble, on the midnight staircase, in the gallery's pale shimmer, in sleep between his wife and his embrace, and always at his own suggestion of a phrase, a dream. His fancy never yet inflicted such a frightful recoil of an offended Heaven. It comes at his own invitation; for he had said in the forenoon of that day,—
"To-night we hold a solemn supper, sir,
And I'll request your presence;"
to which Banquo acquiesced,—