Kaddish.

'MAGNIFIED and sanctified may his great name be in the world that he created as he wills, and may his kingdom come in your lives and in your days and in the lives of all the house of Israel, swiftly and soon.'' The Kaddish prayer in Jewish worship, the counterpart to the Lord's Prayer in Christian worship, punctuates synagogue services. At specified points mourners recite the Kaddish, so sanctifying God's name and affirming God's will even at the encounter with death. When Leon Wieseltier's father died, he undertook to recite the mourner's Kaddish at public worship three times a day -- in the morning, at dusk, and at night -- and he did so for 11 months both in Washington, D.C., where he works as literary editor of The New Republic, and elsewhere.

He tells the story with grace, setting the stage for his reflections on the great issues of life and death, considered through the prisms of memory and grief. These deep thoughts emerge from a dialogue with the great Judaic intellects of the ages, whom Wieseltier knows as companions. The result is a profound work not merely about Judaism but of Judaism. I cannot point to another piece of writing in the English language that accomplishes within -- and for -- Judaism what Wieseltier has here achieved. His book is simply a masterpiece.

Out of his personal narrative of his year of mourning, he time after time leads us to a topic he wishes to consider, walks us through sages' discussions of the problem he has chosen, then takes us through his responses to those discussions, gradually winning our confidence not only in his learning but also, and especially, in his educated judgment. He enlists erudition in the service of the soul. What emerges is a dialogue at the depths of the human experience recorded, in their particular idiom, out of their distinctive perspective, by the Judaic saints of past and present. But what turns learning into literature is the narrative voice -- controlled, spare, restrained -- that Wieseltier has invented for himself.

For example, in reflecting on the theme of inheritance in father -son relationships, he begins with determinism and freedom, the concrete terms in which Maimonides, the great medieval philosopher of Judaism, laid out the problem. Then he intersperses his exposition with a conversation with his bereaved sister, punctuates the lesson with his own aphorisms, tells us how his praying went that day, reflects on tradition, and finally reaches inheritance, turning the topic into the occasion for his own profound reflection. He establishes the tone, austere but delicate, early on and sustains it throughout. Here is a snippet that captures that tone -- smack in the middle of Wieseltier's exposition of a rather recondite rule of public worship:

This morning there were mists blowing through the streets. Georgetown had the fresh, sturdy look of a village by the sea. The familiar houses and lanes presented an unfamiliar aspect, as if the fog were clarifying the scene. The fog was a kind of light. If a fog can be a light, then I am ready to return to my kabbalist. At the teahouse, I read Aaron's discussion of the procedure of the funeral.

As he proceeds, his ''I'' takes on the quality of a ''we,'' as Jewry at every time and place joins in the conversation. He moves the story along, from reflections on dying and mourning in general, to thought about the particular rites of mourning, to martyrdom, all within the circle of holy Israel -- the faith community, not the state or the ethnic group.

That is not to suggest that this book makes life easy for its readers. I wonder whether any masterpiece does. Mr. Wieseltier does not give much guidance, and he demands nearly superhuman patience. His book has no table of contents and no running heads. He never starts a section by telling the reader the theme he will discuss, and he never ends by summarizing what he has said. His readers have to discover for themselves the connections he has in mind between one thing and the next. No college teacher could imagine writing such a book; but Wieseltier is not a college teacher, he is a writer. He does not mean only to communicate ideas and insights. He means, through his art, to affect, to change the reader. And because he pays the reader so high a compliment, demanding so much from his partner in the dialogue, he succeeds.

I wish Mr. Wieseltier had given deeper thought to the idea of the resurrection of the dead. Judaism, like Christianity, affirms the resurrection of the dead for eternal life, and that conviction places death in a different light from the gloom that pervades the secular encounter with it. But in his own way, he has given his father a life beyond the grave, by telling this compelling story. I doubt that many readers will reach the final sections of the book without tears.

The publisher calls the work a ''spiritual journal.'' That misconstrues what Wieseltier has accomplished in this marriage of learning, reflection, and experience. No father ever got a better Kaddish from his son. And no son, in remembering his father, ever formed of the encounter a greater blessing. As I said, it is simply a masterpiece.

Mr. Neusner, a professor of religion at the University of South Florida and at Bard College, is the editor, with his son Noam Neusner, of The Book of Jewish Wisdom (Continuum).