How do I write a monologue for the "doctor" character in Shakespeare's Macbeth?
If you were to write a monologue from the doctor's perspective, it would be vital to include his most important insights. These insights come when he first observes Lady Macbeth to be sleepwalking in Act 5, Scene 1. He has come at the request of her gentlewoman who has seen her repeating the same disturbing motions and the same disturbing words for many nights now.
Having heard Lady Macbeth ask, "who would have thought the old man / to have so much in him?" and "The Thane of Fife had a wife. Where is / she now? What, will these hands ne'er be clean?" he realizes that her "heart is sorely charged" (5.1.41-42, 44-45, 56-57). It does not take a doctor to gather that Lady Macbeth has some terrible weight on her conscience; her gentlewoman has already ascertained as much. The doctor realizes that "This disease is beyond [his] practice" (5.1.62). In other words, he knows that Lady Macbeth does not require a physician, as it is not a physical ailment from which she suffers; she could make better use of a priest because her trouble is clearly spiritual. Moreover, the doctor says that "Unnatural deeds / do breed unnatural troubles. Infected minds / to their deaf pillows will discharge their secrets" (5.1.75-77). He recognizes that the only thing that could have distressed her so greatly is something that goes strongly against her conscience because people who are disturbed by these kinds of troubles will always talk in their sleep. Any monologue of the doctor's should absolutely make reference to all of these revelations.