What is the narrator point of view in Mailer's, Advertisements for Myself?

Advertisements for Myself is narrated in the third-person. Some speculate that the narrator is Sam's psychiatrist: "It is just that I, far better than Sam, know how serious he really is, how fanciful, how elaborate, his imagination can be." But the story also contains considerable skepticism of psychoanalysis and of the jargon psychiatrists employ. Perhaps the narrator is Sam's alter ego, since he knows Sam so well and yet must speculate on the other characters and make suppositions about the situations they find themselves in.