“On The Knocking at the Gate” (1823) is the title of a celebrated essay (it’s below) by Thomas De Quincy (1785-1859) about an event that happens in Act 2 scene 2 of Macbeth. The Macbeths have just murdered King Duncan. Macbeth is horrified by what he has done, his wife less so. Lady Macbeth takes the daggers which he has neglected to leave at the scene of the crime to “gild the faces of the grooms” so as to make them seem responsible for the murder. She leaves and a knocking is heard. She returns and more knocking is heard. Just before the scene ends still more knocking. The next scene moves to the drunken Porter complaining about the knocking. After a succession of knockings at the gate he opens it and admits Macduff and Lennox.

De Quincy essay refers to two groups of murders (The Ratcliff Highway murders of 1812) allegedly committed by John Williams which was said to include a knocking at the door which made him think about Shakespeare’s knocking. He considers the murderer’s feelings during the commission of his awful deed.

But in the murderer, such a murderer as a poet will condescend to, there must be raging some great storm of passion jealousy, ambition, vengeance, hatred which will create a hell within him; and into this hell we are to look.

We were to be made to feel that the human nature, i.e., the divine nature of love and mercy, spread through the hearts of all creatures, and seldom utterly withdrawn from man was gone, vanished, extinct? and that the fiendish nature had taken its place.

Hence it is, that, when the deed is done, when the work of darkness is perfect, then the world of darkness passes away like a pageantry in the clouds: the knocking at the gate is heard; and it makes known audibly that the reaction has commenced: the human has made its reflux upon the fiendish; the pulses of life are beginning to beat again; and the re-establishment of the goings-on of the world in which we live, first makes us profoundly sensible of the awful parenthesis that had suspended them.

To De Quincy, the knocking signifies the return from the dark world of evil to normality. He provides an explanation for the knocking that ends the murder scene and the mundane knocking that irritates the Porter, in the following scene, that goes beyond the matter of fact. His insight into the dramaturgy is believed to be the first, or one of the first, psychological interpretations of Shakespeare’s unique depiction of human behavior and motivations.

Now consider Verdi’s use of the knocking after Duncan’s murder. The knocking occurs just twice, first in triplicate and then in two pairs. They initiate the end of the first act rather than being in the second as in the play. There is no scene with the Porter who does not appear in the opera. Thus, there is no explanation for the knocking other than its dramatic effect as there is no one at the gate. Banquo and Macduff enter after the Macbeths have left. The former discovers Duncan’s corpse. The Macbeths return and feign horror at the bloody deed along with the chorus. The act ends in a glorious ensemble which captures the impact of the murder on the Scottish court and the cynicism of the evil duo responsible for the crime. Here the knocking is not a relief from murder, but rather an awful comment on it. Its effect is like a sledgehammer of doom. Too bad De Quincy never commented on the opera. He lived long enough to have attended a performance of the first version of the opera which like the second depicts the knocking.

The knocking and the finale to Act 1 powerfully conducted by Riccardo Muti are linked below. The pertinent text follows the link.

Macbeth Knocking at the gate and Act1 finale

His spirit is trembling, struggling and raving.
Who would ever call him the unconquered man he was?
Take the knife back there.
Smear his guards with blood
so that they will be accused.

I go there? I cannot go back in!

Give me the knife.

She takes the knife from Macbeth’s hands and goes into the King’s chambers. There is loud knocking at the castle gate.

Every noise alarms me!
Oh, this hand!
The ocean could not
wash my hands clean!

See! My hands are stained too.
A sprinkle of water and they will be c1ean again.
The deed too will pass into oblivion.

There is more knocking

Do you hear? They’re knocking louder.

Come away! We must remove
all suspicion from the murderer.
Be yourself, Macbeth. Have courage!
Don’t be defeated by fear.

Oh, if only I could wipe my crime
from my mind!
O murdered King, if only I could
rouse you from your deep sleep.

Lady Macbeth drags him off.

Macduff and Banquo.

The King ordered me to waken him early,
and it is already late.
Wait here for me, Banquo.

He goes into the King’s chamber.

Oh what an awful night!
Mourning voices were heard
in the blind air, voices of death.
The bird of ill omen moaned gloomily
and the earth was felt to shake.

coming back appalled
Horror! Horror! Horror!

What has happened?

In there,
see for yourself.
I cannot say it!
Banquo rushes into the King’s chamber
Hurry! Ho there!
Everyone come here!
Macbeth, Lady Macbeth, her Gentlewoman, Malcolm and servants all enter.
Murder! Murder!

What sudden confusion!

coming back, stunned
We are lost!

What is it? Speak!
What has happened?

King Duncan has been murdered!

Open your mouth, hell
and swallow all creation in your womb.
Heaven, let your flames fall
on the unknown, detestable murderer.
God, you can look into our hearts,
aid us, we trust in you alone.
We look to you for light and counsel
to tear through the veil of darkness.
Deadly castigator let your formidable,
ready anger take the villain
and mark his head as you marked
that of the first murderer.