The dagger must remain invisible to the audience to emphasize evil’s manipulation of rational thought because it adds to Macbeth’s portrayal as insane, to the tone of confusion, and to the idea of obscuring sight and feeling. Macbeth gradually loses his sanity as the murder and guilt overwhelm him; his brain becomes “heat-oppressed,” since it can no longer think clearly (2.1.51). When one uses apostrophe in such a way that one begins a conversation with an absent, inanimate object, insanity derived from anxiety ensues. Speaking to a dagger is a mentally abnormal behavior that violates a social normality representing the endangerment of others defining insanity. Also, as Macbeth speaks, he is personally confused as to if the dagger is tangible
