WHEN CARTER WILSON '63 taught writing at Harvard several years ago, he hung a small, hand-lettered sign in his office to encourage the hopeful young writers who came to see him. "Be no more ashamed of a story that you've written than of a dream that you've had," said the sign. It was reassuring to student writers blushing over tales of a shattered high-school romance and the wine-dark sea. Gradually Wilson prodded us into replacing our sheepishness with that special curiosity reserved for dreams the morning after. And soon he had begun to teach us to watch for inspirations for our stories just as before we had searched for the sources of our dreams.

Carter Wilson's A Green Tree and a Dry Tree is, not surprisingly, as much a work about the sources of fiction as a work of fiction. Like any novel worth reading more than once, it has more than one story to tell. First, it is a portrait of Pedro Diaz Cuscat, a Tzotzil Indian who, though educated by white Dominicans, became a visionary and rebel who led his people against the priests and soldiers of their white masters, in the 1870 rebellion known to Mexican historians as "The Chiapas War of the Castes." But in recounting Cuscat's story, Wilson also details how he, as novelist, tracked this story down, searched it out in historical documents and folk tales, came to understand it by studying social custom and innuendo, and finally realized its meaning for his own life.

This process is initially set forth in a series of interludes between Wilson and an old man in Chamula, a cargoholder named Juan Tushim, whose grandfather had served Cuscat. "I learned what I know from him," Tushim tells Wilson. "At the middle of the day when the sun stops in the top of the sky, my grand-father would not speak because then God says the names of the sinners, and my grand-father would hear." The rapport between Tushim and Wilson gives the novel a genial immediacy, spiced by curiosity about each other's personal life. ("'In your country in the night,'" Tushim asks the novelist," 'how many times does a man work it with his wife?'") The dialogue between the two storytellers is allowed to intrude much as the pipes in a building by LeCorbusier--to emphasize structure and remind the audience of the creative process itself.

TUSHIM'S TALE--beginning with Cuscat's nativity, following him through his early spiritual indoctrination from his parents, Antun and Rosha, and later from the Dominicans, and concluding with his maturity as a visionary and revolutionary leader--unified the various historical, anthropological and folk sources which the novelist consulted and which he includes as notes at the back of the book. Two of the most haunting scenes in the novel have analogues in this source material. One, recorded by Harvard anthropologist Evon Vogt, is a myth from a town near Chamula, which explains how a bull was present when the Christ Child was born and with its breath and body heat kept the child from dying from the cold. Wilson adapts this myth for the tale of his own hero's nativity. The newborn Pedro is lying in his mother's arms, when his father's bull breaks out of its pen and, as in the earlier myth, keeps the pair alive. Later Cuscat's followers will believe that the bull must have been his soul come to save him.

Another scene finds its source in an unsympathetic rendition by the Mexican historian, Vicente Pineda, of a crucifixion by Cuscat and his followers of one of their own people. But in the context of the novel, the crucifixion of Pedro's brother, Salvador, who is already a very sick man, seems a natural act of piety. And though afterwards Cuscat realizes that to the Dominicans his people dancing in frantic circles are only blasphemous drunken Indians, to him, their leader, they are "drowning people going toward a core which doesn't even have a name, certainly it is not called any god's name, just the place where everything comes from, life and death."

THE HISTORICAL and mythical material is constantly enlivened by the author's own eye and ear for the social customs of the region. He switches easily from the details of daily life--Pedro watching his kint on her knees grinding corn--to those of religious ceremony--Pedro helping prepare the food to be buried with his father. But his special sensitivity is his knack of combining the ordinary with the lofty, comparing the ecstasies of the saints, for instance, to eating chiles ("The heat is fine for a time, but afterwards the discomfort in the back field is too great.") For Cuscat, as his Dominican teacher tells him, is "one of those who can hold opposites comfortably in his head." His natural response to a visitation from Santa Rosha is not awe but laughter. "We speak of God," the novelist explains, "the Indians speak to Him."

If historical and folk sources help provide the novel with its setting, pictorial images--paintings, photographs, film--give it its drama. There are moments when even the characters realize that a scene they are enacting would make an impressive page of art or a vision in the Bible--a white woman walking through a market full of Indians, for instance, feels like the angel looking for Jacob in a desert encampment of unbelieving women. And several times, Wilson mentions visual images that have stirred his own imagination--a curled brown photograph of Juan Tushim's grandfather, a scene in Bunuel's Las Hurdes in which a plain child's coffin is carried down through Spanish passes on the shoulders of grieving relatives. "The rendition of death is liquid," he remembers, "the camera turns and dances, the river ruffles at the men's legs." If this description--with its stark imagery and fluid camera work--is reminiscent of a dream memory, it is by no means coincidental. For the language of dreams mediates between Cuscat's life as he actually lived it and Wilson's imaginative portrait of this life. The documents and folk tales, the social details and visual images only let him help the reader see and hear the story. To help us understand it, he must relive the story through dreams. "For whatever the reason," Wilson explains, "a story comes to have particular weight for us, its equations are, for a time, our equations. We dream it. And so we bear the story a while, until its burden becomes less."

MUCH AS the novelist bears the burden of his hero's story, his hero bears the saints' burden with the language of visions. All are gently recounted, from Pedro's boyhood dream that he has the power to bring frightened souls back into the body to his adolescent dreams which confuse the events of his own life with those of Christ and the saints, to the dreams that fill him with enough strength to lead the insurrection. For though political and social historians may begin to explain a revolutionary as a political and social actor, only a novelist can see into a man's dreams and breathe life into him. In a more modest way, Wilson repeats--Cuscat's visionary insights crossing back and forth over the borders of dreams with ease, and like his own hero, he sees how life might be.