The Villain and the Hero, Acting "As if"

Humans are susceptible to suggestions. We will readily believe things we are told. There for the audience does not need characterization because it will be provided in the script by the author. Okay yes this I understand and I can agree with for the most part.
Acting "As If" did not feel like any new information. Mamet says to use your insecurities on stage. Don't use technique. As an actor you don't need faith. Mamet also talks about actors feelings of being a fraud. I enjoyed and understand the ideas of acting out fantasies for a one person audience. It's true this is easy. You don't need to prep yourself to act out your fantasy. But I feel the difference is that your fantasy is tailored to you. You are not granted this luxury with a play.