Ambitious, eccentric epic in the mold of Dante; Scripts for the Pageant, by James Merrill. New York: Atheneum. $8.95 (paperback).

"Scripts For The Pageant" is the last volume of James Merrill's visionary trilogy -- taken as a whole, a poem over 500 pages in length. When "The Book of Ephraim," the first section of the poem, appeared in 1976, Merrill asserted with a straight face that the work was the result of a long period of communication with the "spirit world" by means of a tea cup and a Ouija board. With his companion, David Jackson, the poet was guided, he said, through a primer course in mystical cosmology by Ephraim, a first-century Greek Jew. The "lessons" and "voices" they encountered (impeccably polished) comprise the poem. The volume earned Merrill a Pulitzer Prize.

The second book-lenght installment, "Mirabell: Books of Number," received a great deal of acclaim and a National Book Award. The "spirit world's" lack of credibility notwithstanding, the poetry of this trilogy has been given a most auspicious welcome.

The desire to create a full-length epic-poem has been the preoccupation of many American poets.Only time will tell, but Merrill's trilogy may well be the most successful contemporary effort in this genre.

Its framework is something of an up-to-date version of Dante's design: a man (in this case, two men) being guided slowly through the trials and revelations of a realm of spirits -- witnessing there reflections of human civilization as well.

Merrill intends that we remember the links with Dante; "Ephraim" appeared a collection wryly titled "Divine Comedies." And the words of Dante, as well as of Milton, and Blake, play a part in Merrill's overall composition.

At the outset, Merrill describes the sort of timeless myth he wished to create: Fed up so long and variously by Our age's fancy narrative concoctions, I yearned for the kind of unseasoned telling found In legends, fairy tales, a tone licked clean Over the centuries by mild old tongues, Grandam to cub, serence, anonymous."

"Scripts for the Pageant" does indeed attempt to do nothing less than epitomize the whole of man's striving to comprehend his role in the universe. And the work does culminate in a sense of wondrous coexistence, wherein the ancient world and the 20th century are embraced in a single design.

While in "Ephraim," we receive broken and halting telegraphy from "the beyond ," and in "Mirabell" voices speaking in dialogue and broad visions, Merrill chooses in "Scripts" to give us the spirits talking in clear, fluent conversation.

Though the repartee occasionally takes on a pompous tone, and some of the angelic scenes smack of Cecil B. de Mille staging as Merrill and Jackson make their way through a heavenly hierarchy, the relationships between the two mediums and their various guides are as subtly drawn as those in any modern novel.

"Scripts" could be likened to an epic radio play, broadcast from the heart of creation. And, like the best of radio drama, the poem draws on two bottomless creative storehouses: The first is an unlimited cast of characters and special effects. (The principals who step up to the celestial microphone include W. H. Auden and Maria Mitsotaki; the Angels of Light, Water, Earth, and Death; the Nine Muses; Homer, Aknaton, Montezuma and friends; Richard Strauss, W. B. Yeats, Gertrude Stein, Pythagoras, and a unicorn from Atlantis.) And the second is the reader's imagination.

Merrill's vision is presented without the benefit of color television close-ups or the cinema's slow camera pans. The voices come; wem are responsible for visualizing the scene. Line by line, wem must explore the images of all we've ever seen and dreamt in order for Merrill's creation to take form. This is the true conjuring power of poetry, and "Scripts" uses it as skillfully and dramatically as any verse of this century.

All this concerns the "how" of what the poet has to say -- and few writers of the English language work with a more finely developed craft than Merrill. He moves from bardic tones and rhymed couplets to the acerbic wit and passionate lyricism of the contemporary voice.

But the "what" and "why" of this trilogy are the driving forces that rank the poem a work of genius. The subject matter is no less than the nature of the entire creation.

Unquestionably the poem's warnings and challenges are deeply-felt -- and they seem at once timeless and as relevant as the morning headlines. In a day when hard-edged cynicism and submerged emotionally are worn like proof of intellectual capability, it must require courage to brave the terrain Merrill explores here.

Of course, many readers will be put off by Merrill's claim taht the book was dictated from a "spirit worls." Others, I'm sure, will admire the poetics of the work apart from the ideas presented. The touchingly understated love that binds the two narrators is yet another dimension that will attract attention.

But "Scripts for the Pageant" must be seen as the last link of a bridge that attempts to span all of these concerns, and travel still farther on.