Question

what evidence leads you to believe that the dagger macbeth sees is an illusion?

Answer 1

The line "A dagger of the mind, a false creation" is an evidence that the dagger Macbeth sees is an illusion. This means that Macbeth has very strong imagination which is primarily in control of his mental suffering all throughout the story.

Answer 2

Answer: A false creation, / Proceeding from the heat-oppressed brain?