What is the main theme of Act 5?

One of Act V's main themes is death. Of the four deaths that occur in the final scene of the play, only one – Hamlet’s – is planned. The other three are, if not senseless, at least spontaneous and chaotic. The entire gory episode seems to be a playing-out of Hamlet’s new understanding of the world – death strikes randomly, senselessly, absurdly. The only meaning that matters must be made out of apparent meaninglessness. Hamlet’s dying words, in fact, are a plea to his friend, Horatio, to help the court audience sort out the carnage that they have seen: “[I]n this harsh world draw thy breath in pain, / To tell my story.” Hamlet emphasizes that significance comes only in retrospect, with storytelling, with sense making, not in prospective action. His death thus demonstrates the value of introspection over action, and the triumph of thought over fate, against the uncertainty and confusion of death.

For more information on this theme, follow the link below to Gradesaver's theme page, where the theme of death is covered in detail

http://www.gradesaver.com/hamlet/study-guide/themes