In agreement with all the above, perhaps we should take a look at the title as well.
A number of characters in Shakespeare's plays could be called "princes of darkness." Some examples are Hamlet, Macbeth, Coriolanus, Othello... The dark crevices of their hearts and minds were instrumental to the tragic endings that the playwright succeeded in achieving.
By contrast, Shakespeare may be aptly called a "prince of light" because he enlightens audiences of all times about the whys and wherefores of human nature. In fact, the whole range of personality, character and motivation, as well as the passions and affects that rule behavior can be found in his works.
Thus, the curtain that he raises is not only the divide between stage and audience, but also one that, until raised, conceals the best and the worst in mankind.