THORNTON WILDER has been dead 10 years and I suspect that his popularity today rests largely on two Pulitzer Prize winners, the 1927 novel The Bridge of San Luis Rey and the play Our Town, which opened in 1938 and has been staged repeatedly since.

That limited appreciation should be enlarged by publication of his Journals, for they show Wilder to have had the most wide- ranging and the best informed literary intellect of his generation of American writers of fiction.

Bookish, some critics said, dismissing him as an unoriginal borrower. (Not, however, so perceptive a critic as Edmund Wilson). He "represents the library," Hemingway told a friend. And it is true that Wilder was uncomfortable if library stacks were not within reach, and that books, along with music and walks, were needed stimulants. What other 20th-century novelist or playwright read as omnivorously and searchingly the literature of the ancient Greeks, the modern Germans, French, Italians, Spaniards, Irish, British and, of course, Americans? Or so meticulously studied Joyce, Kierkegaard, Goethe, Gertrude Stein, and Lope de Vega, creator of the national theater of Madrid in the 16th and 17th centuries and to whose plays Wilder devoted a thousand journal pages? Or who "heard" music by reading scores, pouring over the masses of Palestrina in the early hours of the morning? I'm not sure what it says of American impresarios that Wilder's opera, The Long Christmas Dinner, set to music by Paul Hindemith, has been heard only once in the United States, in 1961, and that a second opera, The Alcestiad, with a score by Louise Talma, has never been performed in this country.

Yes, he was a man of the library, and understandably his teaching years in the 1930s at the University of Chicago in the Great Books era of his Oberlin and Yale classmate, Robert Maynard Hutchins, were his happiest. His wartime play, The Skin of Our Teeth -- which addressed the question of what happens when a human being is made to bear more than a human being can bear -- is climaxed by quotations from the great philosophers. He was forever after the Big Idea, the timeless and universal lodged in particular incidents and characters. Our Town is not about life in a New England village in the 19th century; it's about everyman, everywhere. Settings for his stories mattered little -- Caesar's Rome, a Greek island in the century before Christ's birth, the ice age or 18th-century Peru (a country he hadn't seen when he wrote The Bridge of San Luis Rey). What difference did it make that only two of his novels -- The Cabala and Heaven's My Destination -- have backgrounds with which he was personally familiar? He was not writing autobiographically, as Scott Fitzgerald did so brilliantly.

EXCEPTING 18 months in Arizona completing his next-to-last novel, The Eighth Day, Wilder was constantly on the move; journal entries were jotted down in hotels, aboard ships, at the MacDowell Colony, or his desk in Hamden, Connecticut. The most congenial place of all for composition was a nearly-deserted resort off-season -- Atlantic City, Newport, Quebec, or Zurich.

Only a third of his journals are included in this volume, and there are no plans for another. All were written for an audience of one, Wilder, and not intended for publication. The journal was his mental exercise mat where he wrestled with ideas about craft. We miss here many passages of introspection and self-analysis, which were excluded, though not all. Thus: "I must shake my whole self and learn what I do and do not believe." And, "I try in life not to hurt a flea, but . . . I find that I understand cruelty in myself as separated from Iago's and the Nazi's by degree only, not by kind. Its presence in myself is not so absolute but it springs from . . . moral laziness, self-indulgence, self-importance -- things for which I am furnished with the material for self correction." Wilder was unsparingly self-critical, yet there are no traces here or elsewhere in his work of morbidity or despair. "We must take ourselves as we find ourselves," he wrote, "always hoping for some improvement but accepting the basic cast of the die."

A number of the notes were efforts to clarify and organize in publishable form (an unfulfilled ambition) thoughts he had put forward in lectures at Harvard. He knew that the spoken word is governed by less strict laws than the written. Throughout, there are illuminating passages on the nature of storytelling, Victorian morals, pessimism and optimism, the actor's temperament, the Audience (how hard Wilder strove for "invulnerability to the valuation of others" and how insistent the needs and opinions of others were), to Melville ("the ever-youthful surprise that there is evil in the universe"), Hawthorne ("those unloving demanders-of- love are spoiled children who want in perpetuity the being-loved condition of infancy"), Veblen ("he doesn't hate -- which is self-forgetting, he merely despises, which gives him a sort of sluggish self-satisfaction") and Gide ("all his vast intelligence is falsetto -- doubly tragic because his life is one long sincere effort to be sincere").

Two short sketches from and notes on The Emporium are tantalizing hints of what Wilder hoped to make of this combination in play form of the atmosphere of Kafka's The Castle and a Horatio Alger theme, but for which he could invent no last act.

An appreciative preface to the Journals is provided by Isabel Wilder, who was indeed her brother's keeper and came as close as anyone could to being his confidante.