This is the very painting of your fear;
This is the air-drawn dagger which, you said,
Led you to Duncan.
(2) The Ghost seems to be created by Macbeth's imagination; for his words,
now they rise again
With twenty mortal murders on their crowns,
describe it, and they echo what the murderer had said to him a little before,
Safe in a ditch he bides
With twenty trenched gashes on his head.
(3) It vanishes the second time on his making a violent effort and asserting its unreality:
Hence, horrible shadow!
Unreal mockery, hence!
This is not quite so the first time, but then too its disappearance follows on his defying it:
Why what care I? If thou canst nod, speak too.
So, apparently, the dagger vanishes when he exclaims, 'There's no such thing!'