A literary cliché
meaning imagination, sometimes in the form of a supernatural or fantastic vision; also, a prophetic impetus
to enact an idea.
Taken from Shakespeare's Macbeth, a reference by Lady Macbeth to her husband's haunted vision of a knife suspended in mid-air; a reproach for his present unrest at seeing an apparition:
This is the very painting of your fear:
This is the air-drawn dagger which, you said,
Led you to Duncan.
--Scene iii, act 4