What is the subject of Hamlet's speech in Act 2?

In Hamlet's soliloquy in Act II, he muses about the strangeness of his situation. He asks himself, “How can this player be so filled with grief and rage over Priam and Hecuba, imaginary figures whom he doesn’t even know, while I, who have every reason to rage and grieve and seek bloody revenge, am weak, uncertain, and incapable of action?” He curses himself and his indecisiveness before cursing his murderous uncle in a rage. Having regained composure, Hamlet announces his plan to make sure that the ghost of his father is genuine – that the apparition was not some evil spirit sent to lure his soul to damnation. He declares his intention to stage a play exactly based on the murder of his father. While it is played he will observe Claudius. If the king is guilty, Hamlet figures, surely he will show this guilt when faced with the scene of the crime.