Final answer:
In the soliloquy from Shakespeare's play, 'he' refers to the actor observed by Hamlet, who is moved by the story of Hecuba, contrasting with Hamlet's own struggle with inaction and emotional turmoil.
Step-by-step explanation:
The referent of 'he' in the quote '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?' is Hamlet. In this soliloquy, Hamlet is comparing himself to an actor who could summon tears for Hecuba, a character in a play, questioning why he himself does not show the same passion concerning his own situation. The 'he' Hamlet refers to in this context is the actor he has been observing, who is moved to emotion by Hecuba’s story, while Hamlet struggles with his own lack of action and intense emotions regarding his mother's and uncle's actions, which have directly affected him.