The Decline and Fall of the Human Race : THE CHILDREN OF MEN: By P.D. James (Alfred A. Knopf: $22; 256 pp.)

There is but one liberty: to come to terms with death, Camus wrote, after which all things are possible.

It is not individual death that James confronts in her new novel but the potential death of the human race itself. Suddenly, mysteriously, humankind has stopped bearing children. Values have collapsed. Apathy blankets what activity remains.

There is, of course, no art; museums and all our grand ambitions stand unattended; government-sponsored porn shops attempt to flog what sexual, creative drive lies dormant. “Human mules deprived of posterity,” men and women endure the rag ends of their lives. Women push dolls in elaborate prams about the streets; men preserve what empty social forms they can. In a few the sense of despair is so great that they ally themselves to horrendously doomed causes.

The stage is set, then; we are prepared for a sweeping, perhaps ultimately poetic evocation of mankind’s twilight, something in the vein of Stapledon, or of George Stewart’s “Earth Abides.”

What would society be like, what might it become, or unbecome, under absolute sentence of death? Able to pass nothing on, unable to reproduce itself even symbolically, without social structures to place and hold us in place, what reasons could humankind find for going on?

Unfortunately, P.D. James fails to follow through on the implications of her theme and instead elects to let it all down into a curious meld of melodrama and religious symbolism. The impending birth of a child--immaculate, one might say, since no explanation for this reversal of mankind’s barrenness is offered--brings on a flurry of religious referents: the manger-like shed where the birth takes place, the ritual killing of the father, the pursuit by authorities, the personal sacrifices and martyrdom of those close, even the betrayal by one “disciple.”

Something beyond mere habit draws readers to genres such as the mystery or science-fiction. With the latter, sometimes called a literature of ideas, the attraction is often the genre’s potential for concept, and all too often this has led to a fiction in which characters are carried off on the runaway horse of plot.

When writers veer toward science-fiction, as mystery novelist James does here, it’s precisely this idea that beckons, and however fine these writers are, because they have little idea of what has been and is being done in the genre, because they’re overwhelmed by the sheer amplitude of what they are essaying, the results are often disappointing.

Writing of dystopias casts these difficulties into further relief. Few non-genre writers even recognize the need to imagine, truly imagine, an alternative society; fewer still have the imaginative power and discipline to do so. Because of this, virtually all mainstream dystopias (along with most genre ones, I rush to emphasize) come down simply to some thwarting of individualism and, with its re-trumpeting, restoration of an order remarkably like the one we’ve got. Thesis, antithesis, status quo.

Squarely in the British tradition, James is a master of character and contributing incident, her novel from first to last exceedingly well-wrought. Its primary pleasures are those of craft: a deft interleafing of lives, the reflective interaction of first-person and omniscient point of view, the sure voice and pace, the seamless narrative.

“Children of Men,” is, too, an elaborately figured novel. There is, first, the religious undertow. An ongoing, almost programmatic political discourse winds its way throughout. A man’s killing of his own daughter flows into the murder of one woman’s doll by another jealous woman on the street, and this in turn on to the birth of the new child. The novel’s early elegiac tone is quite beautiful: equal measures of celebration and sorrow, a sadness for all things unsaid, undone, forever unredeemed.

It’s at the very point this tone shifts that the novel falters, exposing a hollowness more distressing than its decline into melodrama and conventional territory.

Since useful works of art rarely are about what they seem to be about, then we must wonder, finally, whether “The Children of Men” may not be at its deepest level a kind of eulogy for Britain and for a way of life that James recognizes is gone. Her metaphor of a world from which the life force has departed, her portrait of a final, declining generation, even the novel’s polite, dissembling language, suggest this.

To every appearance, James set out to provide a cosmic poem; considered for a while folding in the makings of a political novel; decided somewhere along the way to interpolate a religious fable; and ended up with a book that’s none of these, but a kind of sympathy card for her own time and class. Relics of empire thick on the tea cozy, as one poet put it . . . however beautiful the relics, however fine and bracing the tea.