What is the chief focus of the Theatre Laboratory in the book, Towards a Poor Theatre?

This is Polish theatre producer Jerzy Grotowski's school of theatre which aims for a "poor theatre" to differentiate itself from film and television. It has minimal props, costumes, make-up, lighting, and scenery, just enough to communicate essential meanings. The chief focus of the Theatre Laboratory is the actor, and the communication between actor and spectator. Because of the importance of this communication, the barrier between actor and spectator is constantly challenged.