A question asked without expecting an answer, because the answer is already implied, or because what matters is the doubt it exposes.
In Hamlet
For Hecuba! / What's Hecuba to him, or he to Hecuba, / That he should weep for her? What would he do / Had he the motive and the cue for passion / That I have?
“What is Hecuba to him...?” and “What would he do...?” are questions whose answer Hamlet already knows: the actor weeps without cause, and he, with cause, does not act. The doubt exposed is his own.
Act II: Feigned madness and the theater trap, Hamlet, alone
That cannot be, since I am still possessed / Of those effects for which I did the murder: / My crown, mine own ambition, and my queen. / May one be pardoned and retain th' offense?
Act III: The Mousetrap and the death of Polonius, Claudius, alone
How stand I then, / That have a father killed, a mother stained, / Excitements of my reason and my blood, / And let all sleep
Act IV: Exile, madness, and the trap, Hamlet, alone
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