Perhaps the world's most famous mental patient, Hamlet's sanity has been argued over by countless learned scholars for hundreds of years. As a mere student of advanced-level English Literature, I doubt I can add anything new to the debate in 2000 words, but I can look at the evidence supporting or dispelling each argument and come to my own conclusion.
Hamlet is obviously experiencing grief and despair right from the beginning of the novel, with the death of his father and his uncle's seizure of the throne and rapid weddign of Hamlet's mother, and we can observe his great grief bordering on irrational suicidal tendencies as early as Act II Sc I, where he gives his first soliloquy. He cries:
'O that this too too solid flesh would melt,
Thaw, and resolve itself into a dew!
Or that the Everlasting had not fixed
His canon 'gainst self-slaughter!'
Macbeth wants his flesh to dissolve into a dew ('solid' contrasting with 'melt' in the first line), and wishes that God had not forbade suicides from going to heaven.
This is also the first glimpse of another recurring theme in the play, that of Hamlet's unhealthy obsession with the afterlife. This is one of the reasons that the ghost of his father has such an effect on him, which is a trigger for all the subsequent events in the play.
Moving on to the fourth scene, the next interesting speech is on l. 23. It is a long and complicated speech, but its general gist is that if a person has one fault, no matter how virtuous they may be in other ways, they are soiled by 'the stamp of one defect'. This speech is quite ironic, because it is Hamlet's 'one defect' (his hesitancy and inability to take action), regardless of his...