HERE is Norman Mailer, peeling the skin off his own body, scraping the underside of his skin with pin pricks. And here is Norman Mailer, mythmaking, raising himself to new celestialities, o you Sergius O'Shaugnessy.

Mailer's book-length piece in this month's Harper's Magazine, "On the Steps of the Pentagon," is an orgy of self-flagellation and self-exaltation, with the one and the other glowing intertwined in a kind of frenzied chromosomal spindle. "The Steps of the Pentagon" is the ultimate realization of Mailer's one great talent--masturbation--the quintessence of self-love and self-debasement.

Ostensibly, the piece is journalism (whatever that means). It is a long, digressive, discursive account of how Mailer (he refers to himself, his protagonist, in the third person throughout) gets invited to this March on the Pentagon, and how he goes to Washington and marches on the Pentagon and gets arrested for "transgressing a police line," as he tells a reporter (me, in fact), and how he goes to jail and gets tried and gets out of jail and goes home and decides to write about his adventures for Harper's Magazine (hello, Norman Mailer).

The reason "The Steps of the Pentagon" is Mailer's best work, as Harper's boasts on the cover, is one magnificent ten-page passage about Thursday Night at the Ambassador Theatre. Time Magazine described the scene in a red-bordered box last October, telling how Mailer slurped bourbon from a coffee mug and yelled obscenities at the audience, as Mitchell Goodman, Robert Lowell, and Dwight MacDonald--the other speakers--sniggered at him patronizingly in the wings.

Mailer quotes the Time story in its entirety at the beginning of his article, then writes, "Now we may leave Time in order to find out what happened." Mailer really tells us, and he is far more merciless on himself than Time.

After the audience has deserted Mailer, it heaps its affections upon soft-spoken Lowell. Mailer describes his feelings as he watches Lowell perform: Mailer felt hot anger at how Lowell was loved and he was not, a pure and surprising recognition of how much emotion, how much simple and childlike bitter sorrowing emotion had been concealed from himself for years under the manhole of his contempt for bad reviews.

He is a man alone with his ego, holding it limp and spent in his hand, looking at himself in the bathroom mirror of his shame: And in the privacy of his brain, quiet in the glare of all that sound and spotlight, Mailer thought quietly, "My God, that is probably exactly what you are at this moment, Lyndon Johnson with all his sores, sorrows, and vanity squeezed down to five foot eight," and Mailer felt for the instant possessed, as if he had seized some of the President's secret soul. . . .

Later, Saturday at the Pentagon, Mailer again confronts himself. With Lowell and MacDonald, he decides to get arrested. All he has to do is cross the military policy line and the deed is done. "Let's go," he says and walks over the line, not looking behind him. But MacDonald and Lowell stand still. They do not cross the line with Mailer: It was as if the air had changed, or light had altered; he felt immediately much more alive--yes, bathed in air--and yet disembodied from himself, as if indeed he were watching himself in a film where the action was taking place.

THAT kind of description is one that a writer can only write about himself. I saw Mailer cross that line that Saturday and walk up to an MP and get arrested and I took a picture of him. And I thought, "There is Norman Mailer getting arrested in his three-piece pin-striped suit. What a comfortable feeling it is to see Mailer. He makes everything seem so friendly. There is such solace in respectability." But Mailer, at the very same instant, was not feeling the way I had imagined him: The subject was not absolutely calm. To his own excitement was added the tense quivering grip of the Marshal--the sense of breathing mountain air had hardly abated: his lungs seemed to take in oxygen with a thin edge, his throat burned. . . .

As a journalist, I could only describe Mailer as I saw Mailer. But how relevant or how real is that judgment? What counts is how Mailer saw Mailer, for that is what Mailer really was at that moment as he was being arrested. This is the justification for this kind of personalized journalism. It is the answer to the doubt Mailer expresses in his piece: To write an intimate history of an event which places its focus on a central figure who is not central to the event, is to inspire immediate questions about the competence of the historian.

"The Steps of the Pentagon" is a true nonfiction novel. Mailer is eminently a novelist and eminently a journalist--he is remarkably accurate at being both. The combination is a daring achievement. Novak and Evans or Knebel or Galbraith write novels based on contemporary journalistic events, but they are related to their own reality as science fiction is related to science--a fantastic but logical extension of reality. What Mailer achieves is a deep personalization of the event. And his success as a journalist can be attributed to his talent as a novelist. As he writes of himself: . . . he was a novelist and so in need of studying every last lineament of the fine, the noble, the frantic, and the foolish in others and in himself. Such egotism being two-headed, thrusting itself forward the better to study itself, finds itself therefore at home in a house of mirrors, since it has habits, even the talent to regard itself. Once history inhabits a crazy house, egotism may be the last tool left to history.