Why does Hamlet write a letter to Ophelia?
Hamlet has composed a letter to Ophelia for the very best purpose--to convey his love for her! But wait, I thought Hamlet and Ophelia are estranged from each other during the entire play? To solve this confusion, we must consider just who it is that brings the famous love letter to Claudius--the fawning Polonius, who will do anything to curry the king’s favor and prove his own worth.
To investigate, let’s back up a bit. In act 1 scene 3 Polonius orders Ophelia not to speak with or see the prince any more, and she has no choice but to obey him. In act 2 scene 2 she tells Polonius, “as you did command / I did repel his letters and denied / His access to me.” Therefore, she has not received any new letters from Hamlet since before he put “an antic disposition on.” It's possible that Polonius, to add weight to his “Hamlet is crazy for my daughter” theory, takes an old love letter Hamlet had given her. When he tells the king and queen his theory in act 2 scene 2, he vaguely says that Ophelia has obediently given him the letter. They merely assume it is a recent letter.
Although Polonius mocks the language of the letter as he reads it out loud to them, we can hear that Hamlet is quite gifted in rhetoric, something actually considered unfashionable among royalty in the late middle ages, which the play is set in. Hamlet himself tells Horatio in act 5 scene 2 that he once felt somewhat embarrassed that he writes so well, and even tried to forget how. But the skill comes in handy when Hamlet needs to rewrite Claudius’ letter to the king of England, the “changeling” bringing about the death of Rosencrantz and Guildenstern instead of Hamlet himself. It is also quite handy for wooing maidens, it seems.
So Hamlet wrote the letter to express his deep and honest love for Ophelia, something we would never know about if not for those words written by a free and untroubled prince, perhaps before his father ever died. The most convincing lines might be these: “Doubt thou the stars are fire / Doubt that the sun doth move / ...But never doubt I love.” He signed the letter beautifully with, “Thine evermore, most dear lady, whilst / this machine is to him, Hamlet.” He vowed to love her as long as he lived. More so than the question of his sanity, whether he loves Ophelia until his last breath may be the true secret that Hamlet takes with him to “the undiscovered country.”