What is the main conflict in On Directing Film by David Mamet?

In his book, "On Directing Film" famed writer/director David Mamet lays out his theories and his path to them in an informative, straightforward and entertaining manner. Mamet's book is based on a series of lectures before students of the Columbia University Film School. These discussion sessions are an enjoyable aspect of Mamet's book. While they provide a good dose of technical and theoretic information, they give insight into Mamet's style as an open and flexible artisan, characteristics essential for the successful film director.