FRANCO ZEFFIRELLI has fallen victim to the youth movement. In an attempt to tell the story of St. Francis of Assisi as a medieval eccentiric. Zeffirelli runs the risk of presenting the saint as a progenitor of Woodstock nation. His film succeeds in tracing a parallel between then and now, and thereby fails to become an acceptable work of art. At a time when hard-boiled movies are derigeur, a film on a religious theme can appear embarrassingly sentimental. Zeffirelli's has personal interpretation of the St. Francis legend does just that. And at a time when "Godspell" has recently been slapped onto the screen, and the term Jesus-freak is flung at a goodly portion of our "alienated" generation, a modern version of the same legend which stresses the similarities between past and present draws a yawn of boredom without any trouble.

Brother Sun, Sister Moon covers only a short period of the saint's life; his return from the war between Assisi and the rival town of Perugia, his subsequent illness and conversion, the rebuilding of the ruined church of San Damiano, and his trip to Rome to seek advice from Pope Innocent III. Given this limited time-span and the painstaking efforts Zeffirelli makes to focus on the reasons for Francis's conduct, he explains astonishingly little of what was happening in twelfth-century Italy, both according to historical fact and to his own fiction. The war could be any war. A vehicle for top-heavy symbolism, it serves the purpose of contrasting Francis's world-weary pacifism with his merchant father's greedy support of warfare. Zeffirelli uses the presence of militarism in the abstract to furnish crude social commentary as a companion-piece to the attention he lavishes on the generation gap, or on the contrast between organized religion and Christianity experienced according to the Gospels.

He ignores the implications suggested by the community's opinion that Francis came home from the war, not because he was ill, but because he was a coward. His hero wanders silently and rather idiotically from his turreted home to a dye-works in the depths of the slums, and leads the Oppressed Workers out into the sunshine, "because we all should be free like the birds." He throws his father's entire stock of materials out the window into the streets, explaining to his infuriated parent that "all our treaures are in heaven," oblivious to the fact that the impoverished populace he so innocently admires is making haste to grab all of the goods it can.

UNABLE TO DEAL with his son's apparent insanity, Francis' father drags him before the bishop, a portly libertine who cares more about his lunch and his feud with the secular power of the local governor than about the ravings of a boy with a holy mission. His admonitions to refrain from "subverting the established order" ring as hollow as a parody of a dime-store dictator.

In the scene depicted in so many religious paintings, Francis strips himself before the bishop and the townfolk, and hands back to his father his clothes, his earthly possessions and his name. Striding to the city gates, he stands outlined against the sky outside, his naked body reminiscent of the last human nudity Zeffirelli celebrated, the joyous body of Romeo. But his Romeo arose from a bed of love to face a world of tragedy; his Francis rushes off in a return to nature that is too starry-eyed to be believed.

Zeffirelli's adoration of the Umbrain country-side is understandable, but the voice of British pop star Donovan singing limp lyrics as Francis romps his way through masses of poppies and fields of grain turns the story into a musical tour de farce. St. Francis's own documented hymns to his "brother sun and sister moon" bespeak a pious, almost pagan Christianity, inspired by the ballads of the troubadours he heard throughout his youth. Donovan's tunes tinkle with the stilted sounds of AM radio.

Through lush summers and harsh winters, Francis and his group of friends build their "people's church" of San Damiano, under the eyes of a primitive Christ-figure that adorns one of its walls. The "cream of the city's youth" desert the town to follow the companion with whom they once warred and whored, towards a life of charity and chastity.

Their reconciliation with the poor people of the region takes place surprisingly quickly, given the youths' inexplicable behaviour and the resentment they engender as sons of the rich. When they are joined by the prissy prettiness of the future Ste. Clare Judi Bowker), who has accompanied St. Francis on many an interminable nature-walk, any tenuous suspension of disbelief crumbles. Although Zeffirelli spares us cinematic tricks of visions and revelations, his harping on a band of post-adolescent outcasts of society, in search of their lost youth and a Rousseauian utopia, mars the simplicity of the tale just as badly. Treating the legend of St. Francis as a Christian fairy-tale might well have served Zeffirelli's artistic talents better than this poorly conceived Whole Earth Catalogue of the life, loves and politics of Italy's patron saint.

ZEFFIRELLI never quite decides what kind of person his St. Francis should be. As played by Graham Faulkner, he comes close to being a beatific imbecile. But Zeffirelli's own view of him is twofold and confused. With one eye always on the current scene, he marks his man as a rebellious teenager and scatterbrained nature-lover. At other times, he sees Francis as a gentle social critic or potential revolutionary, but because he fails to clarify the conditions against which his crusader is protesting, his message falls-flat. The Pope outrages his decadent court by stooping to kiss the feet that have trudged all the way to Rome, proclaiming that "in our obsession with original sin, we tend to forget original innocence." One of his courtiers recognizes a good thing when he sees it in a more cynical fashion; he believes that St. Francis will be able to bring the poor back to the Roman Catholic church. Both suppositions rest on shaky ground.

With his eye for beauty, his ability to record both pageantry and piety infused with the spirit of the Middle Ages, Zeffirelli almost manages to stage a glorious passion-play. Instead, he drags his characters along like caricatures through a pantomime, sacrificing the magic of a legend to the flatness of a puppet show. Giotto was perhaps the greatest artist to illustrate the life of St. Francis in his frescos at Assisi. Zeffirelli has not been able to prove himself a worthy successor.