Murdoch: journey dazzling, destination uncertain; Nuns and Soldiers, by Iris Murdoch. New York: The Viking Press. $14.95.

Iris Murdoch is sui generis.m She can take a perfectly ordinary love triangle and turn it into an octagon. She can people a novel with enough exotic, talkative characters for 10 books. She can lead lovers through seemingly impenetrable mazes and thickets, which -- amazingly, eventually -- part to reveal the bright light of reason.

All this and more the former Oxford lecturer accomplishes, to great effect, in her 20th novel in 26 years, "Nuns and Soldiers." She sticks with her tried and true recipe, one part major romance, one part peripheral romance(s), one part horror or death, and one part philosophic duel between godlessness and good. The brew is a little weak this time, but it will still delight Murdoch fans.

The plot of "Nuns and Soldiers" thickens like this: When rich, intellectual Guy Openshaw dies in the opening chapters, he leaves behind his idiosyncratic English family (a Judeo-Christian mix) and a beautiful widow, Gertrude.

The Openshaws and their friends are agog as to what man the temporarily bereft widow will choose as a substitute for the impeccable Guy. Will she opt for Guy's old friend, the count, a Polish emigre's son who has striven to be more English than the Crown but is obsessively lonely? The count was Guy's choice. Or perhaps Gertrude will choose cousin Manfred, successful, unmarried, and the family's choice.

When Gertrude seems instead to be infatuated with young, feckless Tim Reede, an indifferent painter without a farthing, the family can't understand her lack of taste and discretion.

In the midst of Guy's loss, a lapsed nun arrives to comfort Gertrude. She is Anne Cavidge, a former college friend, who converted to Roman Catholicism and joined a nunnery. Now, 15 years later and with Guy gravely ill, she precipitately leaves the order and arrives on Gertrude's doorstep. Gertrude takes her in, calling the two of them defeated women. Nothing could be further from the truth.

Anne, like the Openshaw tribe, thinks Tim Reede is inferior to Gertrude. But she bides her time like the noiseless, patient spider and becomes indispensable to Gertrude. When she has the opportunity to throw a wrench into the machinery, she does.

It seems that for years Tim has had a bright but disorderly mistress, Daisy Barrett, whom he has neglected to mention to Gertrude. Thus, the possiblity that Tim is a fortune hunter seems sure, and Anne sets off to confront Daisy, who she suspects is Tim's mentor.

Daisy is the outward antithesis of Anne Cavidge, dirty and maniacally foulmouthed. She shares Anne's conviction that Tim and Gertrude are an unholy pair. But she is not a conspirator, and Anne sees that she is both innocent and honorable.

Thus, the two women represent spokesmen for Murdoch's continuing philosophic dilemma. Daisy, seemingly godless, profane and drunken, is revealed as innately good. Anne is the spiritual doubter, seeking good, but always struggling between sacred and profane love.

As Anne confronts what she considers evil, she has a divine visitation. The Son of God appears at her kitchen table, thin, blond, and dressed in shirt and trousers. Anne cries out her doubts; Jesus is comforting, but her attempt to touch him leaves her with a burnlike stigma.

To the reader, this astounding scene should certainly represent a key clue to Anne's future. And in a sense it does, for she opts for a spiritual life in a new country. Yet, with typical Murdoch irony, Anne's future is determined not so much by conviction or sacrifice as it is because of a lack of any other choice.

The resolution of the crises of the other characters -- Gertrude, Tim, the Count, Daisy -- is equally improbable, but engrossing. In "Nuns and Soldiers," no piece of Miss Murdoch's puzzle is allowed to fall under the table.

Like Proust and Henry James, Murdoch transports the reader to the stylish grace of other times and ways, but cleverly never lets us forget the reality just outside the door. A seedy pub or flat are as real as gossip in an elegant drawing room. The rich patchwork of dialogue, and descriptions of costumes, interiors, and nature in minutest detail, are integral to Miss Murdoch's work.

Because literature is important to her, she gives her works a good deal of care. "Nuns and Soldiers" is no exception. It is comical and pessimistic, intelligent, and eccentric. If the ideas are more provocative than the characters, or the plot contrived, no matter. Iris Murdoch's novels are a bit like life: The destination is uncertain, but the journey is, after all, what matters.