What does this line in Macbeth mean? "A dagger of the mind, a false creation, proceeding for the heat oppressed brain"
These lines are from Act 2.1. Here, Macbeth is experiencing what might be a moral crisis. He knows he is about to kill Duncan, but he is imagining what it will be like to actually hold the dagger and carry out the act.
Macbeth is properly horrified by his vision, but then a ringing bell snaps him back to reality and he feels new resolve to fulfill his plan.
Here is the soliloquy:Is this a dagger which I see before me,
The handle toward my hand? Come, let me clutch thee.
I have thee not, and yet I see thee still.
Art thou not, fatal vision, sensible
To feeling as to sight? or art thou but
A dagger of the mind, a false creation,
Proceeding from the heat-oppressed brain?
I see thee yet, in form as palpable
As this which now I draw.
Thou marshall'st me the way that I was going;
And such an instrument I was to use.
Mine eyes are made the fools o' the other senses,
Or else worth all the rest; I see thee still,
And on thy blade and dudgeon gouts of blood,
Which was not so before. There's no such thing:
It is the bloody business which informs
Thus to mine eyes. Now o'er the one halfworld
Nature seems dead, and wicked dreams abuse
The curtain'd sleep; witchcraft celebrates
Pale Hecate's offerings, and wither'd murder,
Alarum'd by his sentinel, the wolf,
Whose howl's his watch, thus with his stealthy pace.
With Tarquin's ravishing strides, towards his design
Moves like a ghost. Thou sure and firm-set earth,
Hear not my steps, which way they walk, for fear
Thy very stones prate of my whereabout,
And take the present horror from the time,
Which now suits with it. Whiles I threat, he lives:
Words to the heat of deeds too cold breath gives.
(A bell rings.)
I go, and it is done. The bell invites me.
Hear it not, Duncan; for it is a knell
That summons thee to heaven or hell.
As Macbeth is walking towards Duncan's chamber to murder him, he speaks this famous soliloquy. He "sees" a dagger floating in the air pointing towards and leading the way to Duncan's room. He is wondering if this vision is real, or merely "a dagger of the mind," something created in his imagination - "a false creation."
He starts the monologue with one of the most famous lines from this play, "Is this a dagger which I see before me, The handle toward my hand? Come, let me clutch thee:--
I have thee not, and yet I see thee still."
The “heat oppressed brain” speaks to Macbeth’s confusion on which course of action to pursue. Duncan has been a fine king and has done Macbeth no harm. However, Macbeth’s own ambition (brought about by the witches prophecies), coupled with the insistence of his controlling wife, is telling him to kill the King and claim the throne. Macbeth has been forced to make a very difficult decision, to kill the king or disobey his wife and own desires.