It was only a matter of time before Philip Roth confronted the pressing question of his President's dick. Over the past five years, through the tragic heroes of an extraordinary trilogy of novels that culminates in this one, Roth has set out to measure what America has become against what it once seemed capable of being. In American Pastoral, he examined the effects of the fragmentation of the family under the permissive pressures of the 1960s; in I Married a Communist, he analysed the fallout of McCarthyism and the shadow it cast on the American soul; and here he ignites his awesome righteous anger for a spectacular assault on his all-time favourite adversary: his nation's sexual hypocrisy. An alternative title for his book might have been Clinton's Complaint.
The Human Stain is set in the summer of 1998, but written as if with posterity in mind. At Roth's side, he says (or at least at the side of his trusty unreliable narrator Nathan Zuckerman), is Nathaniel Hawthorne, and his book shares many of the qualities of Hawthorne's great constitutional morality tales. This, then, is an epochal summer for American democracy, "when the nausea returned, when the joking didn't stop, when the speculation and the theorising and the hyperbole didn't stop . . . when the smallness of people was simply crushing". It was the summer when the country woke up to find that it had dreamed in the night of the brazenness of its impeachable President, and when Zuckerman fantasises about a banner draped "like a Christo-wrapping" across the White House bearing the legend "A Human Being Lives Here". It was the summer when privacy seemed to have died, when gossip held triumphant sway, when, as Roth titles his opening chapter, "Everyone Knows".
This novel is a sustained dismantling of that complacent knowingness, an evangelical tirade against America's love affair with shallowness. It begins with a simple fact: Zuckerman's neighbour, a former classics professor and the dean of the local university, informs him that "at the age of 71 he was having an affair with a 34-year-old cleaning woman who worked down at the college". On that sentence, on the difficulties of even beginning to fathom what the apparently straightforward congress it describes might mean - difficulties that hold a mirror up to Kenneth Starr's preposterous witch-hunting - Roth hangs his entire tale.
The neighbour is called Coleman Silk, and for him, 1998 is memorable for something beside the much- discussed member of the leader of the free world: it is the year of Viagra, which has put Silk back in touch with his gods. ("Thanks to Viagra I have come to understand Zeus's amorous transformations," he suggests. "That's what they should have called Viagra: they should have called it Zeus.") But Silk takes Zuckerman into his confidence about his affair for other, particular reasons: he wants him to write the story of his very contemporary fall from grace. Silk had been forced from his university office two years previously for uttering the single word "spooks", used to describe the spectral absence from his lectures of two black students. The college faculty's politically correct commissars brand the dean a racist, his entire humanist career is erased, his good name destroyed. He has written a book himself about the episode, but he is too close to it, too angry. He wants Zuckerman's critical distance.
At first, Zuckerman resists; he is more intrigued by the renewed vigour of his friend's sex life than his unwarranted public humiliation. But the more he sees of Silk, the more the story fascinates him. For all his candour, Silk, he senses, is hiding something. And that something, when revealed, begins to make everything else fall into place. Dean Silk - polymath and athlete, burning with intellectual energies - is not only not racist, he is not Jewish: he is a black man who came of age during segregation; and because of the paleness of his skin, he decided to live a white lie.
If Roth uses Silk to demonstrate the impossibility of really knowing the motivation of any other human being, he also makes of him a formidable tragic hero. Silk, like the Greeks he so admires, is destroyed by his humanity as it conflicts with the temper of his age: "how accidentally a fate is made . . . or how accidental it may seem when it is inescapable."
Roth unfolds this drama in a spirit of enraged and engaged journalism and with an anger that ranges over everything from the middle-class love affair with organic milk to the treatment of Vietnam veterans. His greatest vitriol, however, is reserved for campus attitudes towards Silk's relationship: having dethroned him they now seek to emasculate him, too.
There is a supreme confidence about Roth's writing, effortlessly engaged as it is with American modernity. He has always been a driven writer, following his obsessions, and those obsessions have invariably brought him back to examining, in his fiercely intelligent way, the health of his nation. At one point in this novel, Silk, returning surreptitiously to his alma mater, overhears a conversation between two young assistant professors. They are talking about what all America is talking about. "In the ass is how you create loyalty," says one. "This is not so much Deep Throat as Big Mouth," says the other. "Still," they conclude, "you have to admit that this girl has revealed more about America than anyone since Dos Passos. She stuck a thermometer up the country's ass. Monica's USA . . ." To borrow the terms of this contemporary Socratic dialogue, if the nation's "sexual terrorist" inserted the thermometer, it is Roth who, here, removes it and holds it up to the light. And there is no other contemporary American writer as capable of such a rigorous diagnosis of what it shows.
Tim Adams works on the Observer