Roger’s Version <i> by John Updike (Knopf: $17.95; 323 pp.) </i>

Like Byron and Hemingway, John Updike stands not just for himself but for a generation. It is the generation of the Fifties; the time of small causes, good taste, individual salvation through personal relationships and, for seasoning, a tablespoon of Kierkegaard poured over a pudding-like stability and set ablaze.

The generation grew older, with a feeling that it was still holding the reins while subsequent generations went off the track--the Sixties--or returned so massively as to turn the track into a rut--the Eighties. On the other hand, the reins were never attached to very much.

Byron died of revolutionary fever at 36; Hemingway, of suicidal depression at 62. Updike, who is 54 and clear-eyed about those empty reins, simply grows darker. “Roger’s Version” is as close to pure misanthropy as anything he’s done, though his other books have had inklings.

Rabbit Angstrom turned melancholy as time runs out, but Updike lengthened the light upon him into a kind of benediction. “The Witches of Eastwick” seemed black to some readers--its petal-like women transformed into middle-aged cactuses--but Updike was entranced with them, and it showed.

He is not entranced with Roger Lambert, the masculine counterpart to Eastwick’s witches; and that shows too. Updike’s religious nimbus curdles when he does clergymen, and Roger is an ex-minister and a theologian. Packed so tight with self-knowledge that not a mite of grace can get in, Roger is evil, though it is the evil of decay, not of willfulness. Or perhaps, only of the willfulness that comes with decay.

Roger is assistant professor at a school of divinity that can only be Harvard’s; and he lives in an old house in a town that can only be Cambridge. Perhaps it suits Updike not to be specific, but he is our master of the details of place, and here he is so exact that the reticence seems ludicrous. It is as if, ordered into disguise, he had selected a mask that covered only the point of his chin, leaving in plain view his celebrated long nose and sad eyes.

Roger lives with his second wife, Esther, whom he married after the loving acrobatics of a typical Updikian adultery. The love has dwindled to exasperation. The same holds true for Roger’s vocation. Adopting the Barth-like position that any worthwhile God must be unknowable, he is quite satisfied not to know Him. Instead, he specializes in medieval heresies.

Into these closed lives squeeze passion and challenge, in the form of two young people. By the end, Roger and Esther have squeezed them right back out again. The book has a number of themes, but perhaps the deepest and chilliest is that in the Reagan era, age is perfectly well able to prevail over youth.

One of the youths is Dale, a graceless computer scientist who comes to Roger for a grant to set up a computer program to demonstrate the existence of God. The second is Verna, the sexy daughter of Roger’s stepsister. She is living in the slum end of Cambridge with an illegitimate baby by a black father; and she needs Roger’s help.

Roger’s battle with Dale is the philosophical heart of the most explicit novel of ideas that Updike has written. Dale is a creationist, though a sophisticated one. In a protracted series of arguments, he sets out the contemporary doubts that scientists have expressed about current cosmologies and evolutionary theories. Updike has done his homework--once in a while, it seems like just that--and expresses prefatory thanks to the likes of Robert Jastrow, Sir John Eccles, Fred Hoyle, Chandra Wickramasinghe and a number of others.

As dense as some of it is, though, Updike is a superb glosser. When Dale is speaking, the non-scientific reader finds extraordinarily plausible his arguments about the unlikely holes and coincidences needed to account for a universe without a God. But he finds equally convincing Roger’s rebuttal that it is senseless to make God rush into every gap that science has so far failed to fill.

Finally--and this is no small triumph for the author--two alternatives come to seem equally unlikely: first, that such an unlikely beast as the giraffe should evolve by natural selection, and second, that God should trouble Himself to make one.

Of course, it is splendid irony for the scientist to be intent on proving God’s existence, and the theologian on rejecting the possibility of such a proof. But Updike takes it beyond irony. It is perfectly natural. The theologian can’t abide having his specialty--faith--made as commonplace as the physics of the seesaw. The scientist can’t abide an enclave posted: “Faith--Keep Out.”

But Dale is much more than an intellectual challenge. To Roger, he is the rival, the son threatening the father, the example of zeal that shames his cynicism. Specialist in heresies, Roger recognizes himself as the heavy hand of the Church suppressing youthful enthusiasms. “Jesus Christ, John the Baptist: Raggedy outsiders. Insiders tend to be villains, like me.”

That is self-knowledge but not conversion. Roger, in a Machiavellian, back-handed way, sees that Dale gets his grant. And Dale all but destroys himself crunching numbers and hoping that God will fall out of them. Meanwhile, Esther conducts a passionate affair with the youth and emerges much refreshed; while he, doubly bamboozled, breaks his heart.

As for Verna, Roger helps her and, eventually, himself. The exploitation is mutual and rather chilly, but there is a lot of savor to it. Updike is extraordinarily skillful at writing about male arousal, particularly when it is middle-aged and reluctant. The quarrels and cross-purposes of Roger and Verna are a knowing comedy of manners between generations. She is tough and naive; he is gentle and concerned and really much tougher.

When finally, considerably relieved, he dispatches her back to her family in Cleveland; he gives her $300 from his bank’s cash machine. “Do you wish any more transactions?” it asks. And Roger punches the “no” button.

That must be the first fictional love affair with an epitaph by cash machine, and it is unreasonably clever. Throughout “Roger’s Version,” in fact, Updike’s cleverness is prodigious. His capacity to interrogate every moment and get surprising answers, his ability to encapsulate, skewer or celebrate in a phrase; all these are as remarkable as ever. He is master of a sheer elegance of form that shows itself time and again.

It can be too much. He keeps interrupting himself. When he stops Roger in the act of fetching cranberry juice in order to tell you why cranberry juice depresses him, it is brilliant. But is it necessary? Sometimes you feel that this radiant rightness of detail, repeatedly exercised, is exercised in the hope that it will attach to the larger dimensions of the writing.

The brilliancies of “Roger’s Version” often make its darkness palatable, but I think ultimately the darkness is a defect. It is more a state of weariness than an act of negative affirmation. There is a heaviness about it; it is perhaps his only novel without a sympathetic major character.

In the title, Updike presumably intends to distance himself from Roger. It is inevitable, though, that to some degree and on some occasions, he appears as Updike’s alter ego. To the degree that he does, the author might almost be writing of his own as well as his character’s despair. For the theologian, despair is the ultimate sin against the Holy Ghost. For the novelist, it need not be. But it makes you worry about the next book.