'. . . there's nothing there except lines of dialogue. If they're sketched correctly and minimally, they will give the audience the illusion that these are 'real people,' especially if the lines are spoken by real people -- the actors are going to fill a lot in. So a large part of the technique of playwriting is to leave a lot out.'-- David Mamet
The Subtext section has been revised and expanded in the new paperback and e-book editions, Playwriting Seminars 2.0.
http://www.vcu.edu/arts/playwriting/