Mamet's forays into narrative essay have always been lousy (as evidence I recommend his book "Some Freaks" which, if the publisher were honest, should be bound in straw to warn the reader of the quality of Mr. Mamet's premises).
Mamet has been an excellent playwright but a playwright is not a philosopher. A playwright simply is able to bring to life unique people who may not have a thorough understanding of their own psychology and, put these characters into situations that demand they act based on their limited knowledge. Philosophy doesn't work the same way.
Mamet as a philosopher does a good job of evincing flawed dramatic character but, sadly, that becomes incoherent philosophy. Mamet is to narrative philosophy as Eddie Murphy is to pop-singing, a competent artist in one arena believing their talent can translate to all expressions. It is embarrassing.
The theater craft invites the practitioner to remove inhibitions so he or she can take emotional risks. Mamet's Meisner-training is a pretty advanced example of the kind of self-centered and reactive process actors indulge. This can lead to art that is powerful because it makes the illusion of pretend seem real but, can also empower the theater artist to believe their emotional response to external circumstance is reality.
Too often, the theater artist over-trusts his or her emotional guidance system and practices solipsism when they think they are practicing logic.
I quit the theater for 10 years because I saw the same in myself and recognized it may be false and shameful. I hope Mr. Mamet can feel the sting of a similar reality but, fear that his awareness that he is "DAVID MAMET" gets in the way of his thinking.