Chiefly among the many many things I take from Brook is his basic and consistent questioning of what the theatre is and why it has value to the human experience. Writing this out, if seems like a common sense thing that most theatre artists would do, but it isn't. Most theatre artists take for granted those basic questions. The focus is usually on the less profound and more practical questions of what is performed and how is it presented.
With this is mind, I came across this beautiful talk Brook gave in 2005 to Tel Aviv University. He displays his amazing and rather mischievous resistance to being considered "a guru." He also formulates his thoughts so clearly and reasons out his ideas so deeply (and without notes).