What are the main ideas of Hamlet's soliloquy in Act III, Scene III?
Act Three, Scene Three opens shortly after the play-within-the-play has finished. King Claudius is wildly unnerved by what he has just seen and now feels that Hamlet may pose a threat to him. Unwilling to continue to deal with the potential risk, Claudius decides to send Rosencrantz and Guildenstern to accompany Hamlet on a trip to England, believing that he will be safer with the crazed boy out of the country.
After a discussion with Polonius about the two's plans to spy on Hamlet in Gertrude's room, Claudius breaks down in prayer, confessing the murder of King Hamlet to God and seeking forgiveness. Hamlet discreetly enters the room intent on killing Claudius, which is when his soliloquy begins.
Watching Claudius, Hamlet realizes that if he kills him during the act of prayer, he will send the murderer straight to heaven:
A villain kills my father, and, for that,
I, his sole son, do this same villain send
Hamlet does not want Claudius to get off that easily, especially since Claudius murdered King Hamlet before the King had a chance to repent his own sins. To allow Claudius to repent when the man he killed did not have that opportunity would seem particularly twisted—a favor rather than an act of revenge:
To take him in the purging of his soul
When he is fit and seasoned for his passage?
Hamlet realizes that he has no choice but to wait for a more opportune moment to kill Claudius, be it when he's engaging in sex or gambling or some other sin. The objective here is to send Claudius straight to hell with his soul "damned and black." Resolute in this decision, Hamlet slips away to meet his mother.