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If you research, you will find a variety of themes ("life messages") that Shakespeare shares with his audience in Hamlet. Revenge is at the core of the play, though Hamlet's quest for such brings about his own death and that of all those even casually complicit in Old Hamlet's death, or who have aligned themselves to Claudius.
There are other themes: mortality (death), chance, illusion vs reality, etc. All of these are important aspects of the play.
However, I also believe that a piece of art speaks personally to each person who experiences it in some way, whether by reading it, in this case, or seeing it on stage.
Hamlet is one of my favorite of Shakespeare's plays, and yet when I try to imagine myself in his place, the themes above do not speak to me. I see a young man, a prince; he is away at college and is told his father is dead. He returns to what was once a happy community for him—with loving parents and a sweetheart—to find that his mother is remarried to his uncle (which is considered an incestuous relationship to Elizabethans...and to Hamlet's character).
Where he had believed his parents in love, Gertrude is now married to his uncle, and when the Ghost appears and charges Hamlet with avenging his death at Claudius' hands, Hamlet is now torn.
First, is the Ghost really his father, or is it some specter of evil there to rob him of his eternal soul should he murder the King without reason. Secondly, Hamlet ultimately realizes how very alone in the world he is.
Seemingly overnight, Hamlet is forced to grow up, and not by getting a job or going away to college, but by taking on a world of murder, deceit and fear. When Hamlet decides to pretend to be mad, he is buying time as well as looking for proof of the Ghost's accusations. His heart, regardless of the truth of the Ghost's words, is broken. He is forced to see the world through new eyes and it crushes his spirit and his heart.
The line that impresses me most with the sense of loss of innocence as Hamlet must be experiencing it is:
"O cursed spite! That ever I was born, to put it right." (I, v, 215-216)
In this passage, Hamlet laments having ever been born, and that by being born, he is confronted with the familial obligation to avenge his father's death. And while Hamlet might wish someone else to take on the responsibility, there is no one else. Ultimately, his uncle's unquenchable thirst for power is the ruin of almost every character in the play.
For me, Hamlet's loss of innocence is a theme that speaks deeply to me.
The theme of revenge is central to the play. The desire for revenge is the driving force behind the plot. Three young men-Hamlet, Laertes and Fortinbras - are driven by a desire to avenge a father's death. However, while they share a common goal, their differing personalities mean that they pursue this goal in different ways. Both Laertes and Fortinbras act as foils to Hamlet.
Hamlet: Hamlet is given the duty of avenging his fathers "foul and most unnatural murder". He promises that he will "sweep" to revenge, but in reality is not temperamentally suited to gaining vengeance because he is essentially a thinker and a man of conscience. "O cursed spite that ever i was born to set it right". Hamlet's soliloquys bear testimony to his reflective nature. In his famous "To be or not to be" soliloquy Hamlet is attracted to the idea of death as an eternal sleep. He acknowledges that "conscience does make cowards of us all". As a thinker and a man of conscience, Hamlet looks for concrete proof of Claudius' guilt before he acts. Even after the Mousetrap seems to confirm the king's guilt, Hamlet hesitates. Hamlet's claim that he does not want to send his fathers killer to heaven is a classic example of his procratination. It seems to be an excuse for inaction. In reality, hamlet, the thinking man, draws back from the idea of cold blooded revenge.
As Fortinbras boldly marches through Denmark on his way to Poland where he will fight for a "little patch of ground", Hamlet is filled with guilt at his own lack of action. Fortinbras is willing to risk his life and the lives of twenty thousand men in the name of honour. In contrast, Hamlet has compelling reasons to act. He acknowledges that his failure to act is the result of "thinking too precisely on the event".
In acts 1-4 Hamlet lacks a balanced personality and is given to extremes. He either acts without thinking(killing polonius) or else thinks so much that he is incapable of acting(prayer scene). All of hs compassionate declarations ("now could i drink hot blood") come to nothing when his passion subsides Hamlet loses the will to gain revenge. By the time he is sent to England, he still hasn't gained revenge.
In act 5 we see a new Hamlet, a man with a balanced personality, capable of thinking clearly and acting decisively. After he returns from the voyage to England, he believes in the power of providence. "There's a divinity that shapes our ends". He understands that the best laid plans can come to nothing and believes that fate will provide him with an opportunity to avenge his father's death. The second important change is Hamleyt's ability to act without being hindered by conscience. He now finally believes that he can kill Claudius. He logically lists reasons why he can gain revenge without hesitation. Claudius killed Hamlet's father, "whored" his mother, took the crown that was rightfully Hamlet's and even tried to have him killed.