What was the cause of Hamlet's madness?
“The Elizabethan theory of madness as demonical possession is well known” – A History of Elizabethan Drama, by Muriel Clara Bradbook, Page 199 (accessible by Google Book Search)
Horatio (warning Hamlet against following his father’s ghost):
“What if it... deprive your SOVEREIGNTY of reason and draw you into madness?”
Hamlet:
“some vicious MOLE of nature in them....oft BREAKING DOWN THE PALES AND FORTS OF REASON”
Hamlet (to his father’s burrowing ghost):
... old MOLE! canst work i' the earth so fast? A worthy pioner!”
A “pioner” was a military engineer whose job was to dig tunnels under the walls of an enemy castle and plant gunpowder there to bring down the walls. (When I was a combat engineer in the U.S. Army in the early 1970s, we were still officially designated as “pioneers,” although I was trained to use atomic demollitions rather than gunpowder.) Thus Hamlet’s father was his mole of nature, burrowing under the pales and forts of his reason.
Hamlet invited his father’s ghost to usurp the sovereignty of his mind:
“thy commandment all alone shall live within the book and volume of my brain”
Later he was, perhaps subconsciously, aware that he had been possessed:
“though I am not splenitive and rash, yet have I HAVE SOMETHING IN ME dangerous”
After he regained his sanity:
“If Hamlet from himself be ta'en away,
And when he's not himself does wrong Laertes,
Then Hamlet does it not, Hamlet denies it.
Who does it, then? His madness: if't be so,
Hamlet is of the faction that is wrong'd;
His madness is poor Hamlet's enemy.”
Who was Hamlet’s enemy, his foe?
“Would I had met my dearest foe in heaven
Or ever I had seen that day, Horatio!
My father!--methinks I see my father.
That evening Hamlet met his dear father, who seemed to be in Purgatory (kind of a suburb of Heaven). His father usurped his sovereignty of reason, becoming his dearest foe.
I believe Shakespeare intended the demonic possession to be merely metaphorical, symbolizing a more realistic psychological conflict. Hamlet was locked in an internal struggle between the humanist values he had acquired by rational thought (influenced by his schooling at Wittenberg) and the bloody thoughts he had been taught from birth by his father. "TO BE OR NOT TO BE"..."so like the king THAT was and IS THE QUESTION of these wars" - that was Hamlet's dilemma.
- Ray Eston Smith Jr
Hamlet from himself taken away
The demonic possession is metaphorical. Shakespeare is using it as a literary device to emphasize that Hamlet is locked in an internal struggle between two distinctly different sides of his personality. When Hamlet is being true to himself, he is "noble in reason," speaking of "godlike reason." When he is under the influence of his father's value system, he speaks of the "pale cast of thought" and says his thoughts should only be bloody (just as he promised that his father's commandment would live all alone in the book of his brain).
But if there is not at least a metaphor of demonic (or rather paternal) possession, how do you explain:
"What if it...deprive your sovereignty of reason"
"thy commandment all alone shall live
Within the book and volume of my brain,"
"I am MYSELF indifferent honest;
but yet I could accuse me of such things that it
were better my mother had not borne me: I am very
proud, revengeful, ambitious," - a good description of Hamlet Sr, not Hamlet Jr.
"For, though I am not splenitive and rash,
Yet have I HAVE SOMETHING IN ME dangerous"
"If Hamlet from himself be ta'en away,
And when he's not himself does wrong Laertes,
Then Hamlet does it not"
I assert that Hamlet is locked in an internal debate between humanist values acquired by thought and education on one side and, on the other side, warlike values acquired by childhood indoctrination and by loyalty to his father. That makes a lot more sense that the usual interpretation that killing the king is "obviously" the right thing to do and that Hamlet is only delaying because he is naturally an indecisive, cowardly, suicidal wimp.