When we are born (Hamlet, 5.1)

As Banquo says to Macbeth, "the instruments of darkness tell us truths."

In Hamlet, this is especially true in the graveyard scene.  Every once in a while, Shakespeare allows a protagonist to step out of his noble robes and, like Odysseus, don rags in order take what is, perhaps, a public opinion poll.  Find out what people know or think, especially about the protagonist.  Two such instances of this occur for sure in Measure for Measure and in Henry V.  Now, in Act 5 of Hamlet, the prince is not necessarily in disguise.  One wonders, then, if the Gravedigger (or Clown) knows whether or not he is actually speaking to Hamlet.  One could make a case either way.  Regardless, the Gravedigger makes a rather profound point regarding that sheds light on both the birth of Hamlet and the madness of Hamlet.  In a passage that most scholars typically use to mark the age of the prince, the Gravedigger says, in response to the question about how long he has been a "gravemaker":

Gravedigger:

Of all the days i' the year, I came to't that day
that our last king Hamlet overcame Fortinbras.

Hamlet:

How long is that since?

Gravedigger:

  

          Cannot you tell that? every fool can tell that: it
          was the very day that young Hamlet was born; he that
          is mad, and sent into England.

Here, an interesting correspondence is made by the Gravedigger between two events, and the result of one of those events, that most likely took place right about the time of the beginning of the play: Denmark's triumph over Norway and the subsequent death of King Hamlet, which is the likely cause of Prince Hamlet's madness, however one chooses to define or describe his madness.  That moment, then, according to the Gravedigger, seems to be the moment that Hamlet was truly born: the moment that he first went mad.   

Call this an "imperial theme," then, for this idea of a connection between birth and madness is not uncommon in Shakespearean lore.  This idea certainly gains attention in King Lear.  No doubt that when the king goes mad, that is when he begins to see the world more clearly, lucidly, perhaps even more astutely.  In a man in rags, his godson Edgar as Tom O'Bedlam, Lear recognizes a "philosopher," "Theban," "Athenian."  What rational man would take for gobbledygook, King Lear, in all his crazy splendor, soon to be arrayed like the wild flowers of the field, is able to deduce wisdom in Tom's windy words.  Even Poor Tom is amazed by this. This becomes most apparent when in Act 4.6 of King Lear, Tom reinforces a point made earlier in Hamlet by Polonius that immediately and aptly precedes Lear's recognition of Gloucester:

          O, matter and impertinency mix'd! Reason in madness! 

Once  Lear states his recognition of Gloucester, he makes the compelling statement that "When we are born, we cry that we are come/To this great stage of fools."  The more we live, the more distracted by the world we become that we don't even realize how foolish it is.  We get pooped and demoralized, according to the Creator of the Universe in Vonnegut's Breakfast of Champions, by "having to reason all the time in a universe which wasn't meant to be reasonable."  O, reason not the need!  The phrase that the Duke of Venice says to Othello comes to mind: the more we "slubber the gloss" the more we lose sight, perhaps, of just how foolish the world is, of how country matters are, because we get too exhausted to even think about it when we have maybe those few precious moments away from the toiling and spinning.  One needs to officially break, go mad, in order to really see it all, understand it all, more clearly.  That is the moment that one is truly born.