And now, Laertes, what's the news with you?
You told us of some suit; what is't, Laertes?
You cannot speak of reason to the Dane,
And loose your voice: what wouldst thou beg, Laertes,
That shall not be my offer, not thy asking?
The head is not more native to the heart,
The hand more instrumental to the mouth,
Than is the throne of Denmark to thy father.
What wouldst thou have, Laertes?
My dread lord,
Your leave and favour to return to France;
From whence though willingly I came to Denmark,
To show my duty in your coronation,
Yet now, I must confess, that duty done,
My thoughts and wishes bend again toward France
And bow them to your gracious leave and pardon.
Have you your father's leave? What says Polonius?
He hath, my lord, wrung from me my slow leave
By laboursome petition, and at last
Upon his will I seal'd my hard consent:
I do beseech you, give him leave to go.
Take thy fair hour, Laertes; time be thine,
And thy best graces spend it at thy will!
Thou and You
In Old English, thou was singular and you was plural; but sometime in the 13th century, English started copying the French manner of speaking that used the plural as a polite form. So, just like vous in French, you became a means of addressing someone formally. There's a lot of status in play with who uses which form, and to whom. You was more formal, so servants would use it to their employers, children would use it when addressing their parents, and so on. It could also be a social or societal divider. You was said to those above you on the social ladder, and then thou in return was used for those below. Likewise lower social classes use thou when addressing each other. Curiously though, thou was also used to indicate a particular kind of intimacy, as when a character might speak to God. With all of this going on, it's clear that changing from thou to you or you to thou in a conversation always conveys a contrast in meaning - a change of attitude or an altered relationship. Sometimes it is as an insult - if someone uses thou to address someone to whom they owe greater respect - and sometimes (as in this episode) it's a sign of dropping formality to express closeness or intimacy.