Winter in Jerusalem <i> by Blanche d’Alpuget (Simon & Schuster: $16.95; 269 pp.) </i>

Every nation that I can think of, except one, has defined itself by virtue of existing. Israel is the exception; it exists by virtue of defining itself.

The distinctive national characters of Britain, France, Russia, China and so on have formed out of particular amalgams of geography and history. Their respective ideas of themselves were formulated as they went along. We may sometimes think of the United States as initiated by an idea--freedom from the Old World order--but mainly it is a country whose character has been assembled by letting itself happen to itself. Our Founding Fathers were great great grandsons, at least.

Existence, to use the old philosophical formula, preceded essence. In Israel, on the other hand, essence preceded existence. Raison d’etre preceded raison d’etat. Israel had a reason for being before it had a being.

Which is why these last years have been so wrenching. There was the shadowing of the old Labor tradition by more purely nationalistic political currents, the rise of Begin and Sharon, the Lebanese invasion, the growth of religion and settler extremisms. These things have shaken, if they have not yet dislodged, the old assumptions of a bristly but humane social democracy where moral argument may not have always prevailed, but was always taken into account.

When Israel questions its essence, it questions its existence. And this is the theme of “Winter in Jerusalem,” an impetuous and provocative novel by the Australian writer, Blanche d’Alpuget.

D’Alpuget’s Jerusalem is a place where everything is in painful flux, and lives and assumptions have been turned upside down. Even the weather is subversive. The truth is that Jerusalem has its winters, and they can be cold. But the city, like the rest of the country, works on an assumption of heat and blue skies.

The Promised Land was promised sun and oranges. Jerusalem houses rarely, if ever, have central heating; people improvise as if winter each year were an annual string of daily exceptions. D’Alpuget uses a piercing wind and the emptiness of the streets on an icy night to say something about a society whose Utopian energy forged its own reality for a while, and which finds reality turning intractable once again.

Through these streets, in unsuitable Rodeo Drive boots, she dispatches Danielle Green, a high-strung, successful screenwriter who is trying to put together a fractured sensibility and a bits-and-pieces life. Born of a mixed marriage and reared in Jerusalem, she and her mother emigrated to Australia at the start of the independence fighting. Her father had kicked them out. The killing of Danielle’s brother by an Arab sniper turned this urbane and sophisticated man into a religious and political fanatic with no use for a frivolous Gentile wife.

Now, in her late 30s, Danielle returns to write a script and to scout locations for a film to be made by a flamboyant Israeli-born Hollywood producer, Bennie Kidron. What she is really scouting is her past. She tries, with no success, to establish relations with her father, who has become an extremist leader bent on expelling the Arabs and rebuilding the Temple. She visits an old teacher, who has outlived her Zionist causes but not her idealism. She has a tormented affair with Bennie. And she is caught up, unwittingly, in a plot by a splinter group of homosexual Arab terrorists.

D’Alpuget, author of “Turtle Beach,” is a gifted writer with an individual and powerful vision of the convulsions of our times. The hyperactive plot of “Winter in Jerusalem” serves to take us into the convulsions. On its own terms, though, it does not work very well. To get these assorted characters and their assorted purposes to move properly, you need cooler architecture than the author constructs. Her strength is to be hot and intuitive.

Some of her characters are shorthand for their own messages. The terrorists--one of them is an old schoolmate of Danielle--are repulsive, menacing and pathetic, but they are caricatures. The ambitious portrait of Bennie as a force of nature who is crass and sensitive at the same time, tries to be larger than life, but comes out simply as enlarged.

Danielle, the book’s driving spirit, is flawed. When we have her churning over her love affairs and her brilliant career and her inner life, she is too crowded to be quite visible. Her emotions are overdressed, as if the author had shirked selectiveness; a sculpture with too little chiseled out.

But to go on with these novelistic defects would be to miss the freshness and energy of the book’s insights. Danielle’s headlong and scattery probing produces extraordinary pictures of the pain of a creative and troubled society whose temperature, always above normal, has turned into serious fever.

Someone leaves a handbag on a bus. It proves to be nothing, but Danielle feels the reaction of her fellow passengers not as relief and solidarity after danger, but despair and withdrawal. Unable to find a taxi at night, she is picked up by a woman driving by. The driver pours out a torrent of talk about the situation. It is one of those electric Jerusalem conversations, full of defiant fatalism and cynicism that masks love. Suddenly, the electricity stops. “Her frankness tipped upside down and became the opposite: inward brooding, resentment.”

The portrait of the octogenarian teacher and former activist has a shining grace. She lives day by day, cheerfully and in the foreknowledge of tragedy. Undressed, she glances at her body, sticklike, in the mirror. “She was platinum and white, like an old moonbeam.”

If there is a touch of contrivance in some of the characters and situations--the movie that Danielle and Bennie want to make is about the last stand of the Jewish Zealots at Masada--there is none in the portrait of Amos and his son, Gideon.

Amos, an old warrior and idealist, is bitter about the new Israel. He deplores the spirit of aggrandizement, the mood represented by Sharon and his followers, the loss of introspection. He wields his own foreboding that Israel will become “just another Middle Eastern state.” He deplores the Lebanese invasion. Yet he can’t accept Gideon’s decision to face a court martial rather than return to the Lebanese front. And to these contradictions, a third one is added. The idealistic Gideon is killed by the terrorist bomb and Amos, getting the news, is all but literally torn apart.

D’Alpuget’s tumultuous sensibility, if it makes her novel suffer through haste and awkwardness, shines through it. “Winter in Jerusalem” stumbles, but partly because its path is an impressive ascent.