What is the significance of the dagger sililoquay

This scene is significant because it is clearly meant to apprise the audeince of macbeth's state of mind...... the descending madness, visions, and their effects upon him. I've always found this soliloquy to be the one that leaves me feeling the most empathy for Macbeth's character. It's quite powerful.

The dagger itself is a symbol of conscience. It floats in the air representative of those things which will take place. The King has not yet been murdered, but the dagger foreshadows his death. Macbeth hasn't yet committed the unthinkable, but yet his conscience is already riddled with guilt. The dagger symbolizes what will be and the darkness that will follow.