In Macbeth, what are the themes in Act 2 Scene 1's soliloquy? What language devices are used to illustrate the themes?
One major theme of Macbeth's soliloquy is guilt. He seems to be hallucinating a dagger, first clean and then bloody, the weapon with which he will kill the king. The imagery used to describe this dagger, especially when it becomes bloody, is one device employed to assist in conveying the theme. Imagery refers to description of sensory material: thus, it can be visual (sight), auditory (hearing), tactile (touch), gustatory (taste), or olfactory (smell). Macbeth looks down at his own, real, dagger, and when his eyes return to the hallucinated one, he says that on its "blade and dudgeon [are] gouts of blood" (2.1.58). He describes the clots of blood that bedew both the dagger's blade and handle; it's a pretty stark visual image that shows us that it is the idea of killing Duncan that has Macbeth so distraught.
Macbeth also employs allusion to convey the extent to which he is aware that he betrays his friend, Duncan. An allusion is when a speaker refers to another text or a character, scene, or event from another text; it is a way for an author to condense meaning into just a few words because the text which alludes borrows from the mood and meaning of the text to which it alludes. Macbeth describes "withered murder" -- personified -- who is awakened by his "sentinel, the wolf" and stalks his prey, so to speak, like Tarquin (a Roman infamous for his rape of Lucrece) with intent to ravine, or rape, her. Macbeth is aware that he preys on a defenseless man -- Duncan is asleep, after all -- and so he compares himself to a rapist who preyed on a defenseless woman. Thus, the themes of disloyalty, betrayal, and injustice are also explored.