Corrupting Power of Pure Emotion. In the beginning of the play, Macbeth respects societal expectations of him and thus falters in his ambitions to commit regicide; only through the influence of the witches and Lady Macbeth does he gather the will to murder Duncan. From this point, however, Macbeth begins to act more and more compulsively, such as when he orders the murders of Banquo and Fleance; in Act IV, he commits himself completely to living based on his bare impulses: "From this moment / The very firstlings of my heart shall be / The firstlings of my hand" (IV.i.168-170). After making this pledge, Macbeth becomes a highly erratic mess of fitful remarks and emotional outbursts, and eventually tosses himself into inevitable defeat at the hands of Macduff after spending the entire play jealously guarding his life and crown.
Internal Struggle. In the first two acts of the play, Macbeth struggles with morality and ambition, trying desperately to reconcile the two. After act two, he struggles instead to reconcile with his regicidal 'new self,' finally failing the task and falling into utter moral darkness and completely abandoning all optimistic perspective, his old "greatness" decaying until his "Tomorrow and Tomorrow and Tomorrow" speech, when he has given up on all hope of self- reconciliation.
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