Any doubt that John Guare's 1990 sharp-edged comedic drama "Six Degrees of Separation" is one of the finest contemporary American plays should be put to rest by the terrific new Broadway revival starring Allison Janney ("The West Wing"), John Benjamin Hickey ("The Normal Heart") and Corey Hawkins ("Straight Outta Compton"). The play (which was adapted into a 1993 film with Will Smith) popularized the idea that everyone in the world is connected by just a handful of people (i.e. "Six Degrees of Kevin Bacon"). But it also displays a class-based society, where an Upper East Side penthouse is a world away from a homeless youth sleeping in Central Park - though not necessarily impenetrable.