In this soliloquy, Macbeth is pondering the murder of Duncan, and the audience sees that he is terribly conflicted by the prospect of murdering the king. One image evoked by Shakespeare is that of a "poison'd chalice" which will return to "our own lips" if it is attained by foul means. This line foreshadows the results of the murder, as Macbeth's actions indeed bring about his own destruction in the end. Macbeth also describes the virtues of Duncan as angelic, and predicts that if he commits the murder:
...heaven's cherubin horsed
Upon the sightless couriers of the air,
Shall blow the horrid deed in every eye...
The imagery of gentle, innocent angels gives way to that of avenging angels announcing Macbeth's evil deeds to the world. In this way, again, Shakespeare uses dramatic imagery to foreshadow Macbeth's ultimate destruction, and his awareness that, even as he contemplates murder as a path to the throne, he is aware of the likely consequences of such a course of action. In fact, he has essentially decided to abandon his plot until his wife challenges his manhood later in the scene.