The Dagger Scene in Macbeth is to be interpreted along psychological lines. It is to be understood that the dagger scene is not a part of the supernatural machinery of the play.
Macbeth is highly excited, it is his imagination what made him believe that he saw a dagger beckoning(calling) him, for Macbeth being a moral coward was unable to accept the responsibility for any decision. He had uptill now depended upon witches and his wife to fool him on taking the decision to kill Duncan. However, now he was alone without support of witches and his wife, who at present was making preparation for the murder of Duncan.
In such circumstances, Macbeth had no choice to take responsibility for action, he was about to take. Since he found difficult to do so, he typically recourse to his imagination which projected the image of Dagger in the air. This seemed to justify the killing of Duncan with a dagger which looked similar to the mission.
The dagger is no more than a psychological interpretation produced by guilty and imaginative mind of Macbeth. He confessed this fact to himself but insignificantly continued to believe in illusion in order to shrung(castaway) the responsibility.
Macbeth was confused by the paradox of his ability to see the dagger and yet not be able to feel it. He asked almost in disbelief : “In this dagger which I see before me, the handle towards my hand ?” He was warmed that he could not catch it and said : “I have thee not yet I see thee still.” He tried to justify his action by commencing himself that since the handle was towards his hand it was an omen sign prompting him to kill the king. Macbeth’s rational faculty however would not allow his imagination to go unchallenged. His rational mind was forced to recognize the vision as being : “ I dagger of false mind’s creation proceeding from heat oppressed brain.”
Even though Macbeth tried to get rid of the dagger from his mind, his imagination could not be suppressed. He continued