ART : They’re Still Glowing : Illuminated manuscripts are the surprising centerpiece of a beautiful, intellectually exciting Metropolitan Museum exhibition on the splendors of Renaissance Florence.

If you’re going to paint a picture about a miracle, then you better make sure the painting is miraculous too. Be cause if it isn’t, who’ll buy your wildly unbelievable story?

“Painting and Illumination in Early Renaissance Florence, 1300-1450” is an exhibition of 94 paintings about miracles. (There are also eight drawings and several examples of embroidery.) Most are, in fact, miraculously compelling works of art.

Because they are, they have something crucial to say about the gradual but decisive shift in European culture that has come to be called the Renaissance. Between the beginning of the 14th Century and the middle of the 15th Century, an entrenched way of looking at the world was slowly being replaced by another, which reverberates to the present day.

This beautifully organized and intellectually exciting show, which recently opened at the Metropolitan Museum of Art, can be seen as a worthy sequel to the Met’s eye-opening 1988 exhibition “Renaissance Painting in Siena.” If the Sienese show suffered a bit from an odd premise, it did bring to the foreground a complex transitional period that has never really gotten its due. The Florentine counterpoint does too.

The transformation that the new show chronicles concerns the world of miracles as represented in Italian art. From our largely secular vantage point today, it’s easy to overlook the fact that the subjects represented in these gorgeous paintings aren’t everyday occurrences. They’re mind-boggling supernatural events.

Fra Angelico’s astonishingly beautiful pair of small panel paintings, which form a breathtaking climax at the end of the exhibition, shows the Archangel Gabriel announcing the Immaculate Conception to the Virgin Mary. Objectively speaking, this is a rather fantastic tale.

Imagine: What the artist has been hired to show is an invisible, winged creature making himself known and whispering an ecstatic message to a shy young girl, informing her that God has impregnated her with his son.

And you thought “Jurassic Park” was a little hard to swallow.

Fra Angelico, however, makes you at least consider the possible veracity of the story. Gabriel and Mary are represented as noble Tuscan youths, irradiated with mystical splendor. Their earthly environment has dissolved into a shimmering golden ground, which merges seamlessly with the elaborate halos encircling their heads. It melts into the magnificent auric wings rising up behind Gabriel.

These fantastic trappings contrast sharply with the motionless, statuesque figures, who are painted as ideal representatives of earthly life. Gabriel points his finger heavenward before his slightly opened mouth, while Mary, eyes lowered and head bowed, crosses her arms before her womb. Their smooth, slightly pinkish, alabaster skin and simply adorned, columnar forms invest them both with a fixed sense of gravity appropriate to the awesome news.

The original use of these panels, which probably date from the early 1430s, isn’t known for sure. The current best guess is that they are fragments of a piece of sacristy furniture from a Florentine church.

If so, their status as furniture decoration enhances a sense of secularism, within which religious doctrine was being absorbed. A central irony of the new Renaissance painting is that, for all its preoccupation with creating believable depictions of a world of miracles, the effort simultaneously announces the arrival into prominence of an increasingly secular culture.

How? Critic Harold Rosenberg once keenly observed that if you inhabit a sacred world, you find art all around you. You don’t make art, because there is no need.

In the sacred world of the Old Testament, where the Ten Commandments were handed down to Moses, such miraculous objects as Joseph’s coat or the burning bush obviated any demand for graven images. That’s why Commandment Two forbade them.

By stark contrast, inhabiting a secular world means that miracles have to be made. One after another, artists in Italy began to make them, and in an unprecedented scope and abundance. “Painting and Illumination in Early Renaissance Florence, 1300-1450” chronicles the advance edge of a newly developing secularization in European culture, with its otherwise inexplicable proliferation of drop-dead paintings.

As with the 1988 Sienese show, the era covered by the current Florentine display is not easily surveyed in a museum presentation. One of the great triumphs of the early Renaissance was the development of large-scale wall paintings. Needless to say, these pose a few problems for travel.

So does the fragile nature of portable wooden panel-paintings, which are another great achievement of Italian art between the time of Giotto early in the 14th Century and Fra Angelico in the mid-15th Century. Wooden panels are especially susceptible to the changes in temperature and humidity that inevitably accompany their shipment between museums. Loans are only made with great caution and for exceptional reasons.

Nonetheless, Metropolitan cu rators Laurence B. Kanter and Barbara Drake Boehm have managed to pull off an important and convincing exhibition, which goes a very long way in articulating a fundamental shift in European culture. They’ve done it by taking advantage of their own prodigious resources--12 of the 30 panel paintings on view are from the Met’s own collections--while several other museums in the United States and Italy and a number of private collectors have been generous with loans. (The show won’t travel after closing in New York.)

More significantly, however, the curators have accomplished the task through wholly unexpected means: The show traces early Florentine painting principally through manuscript illumination. The assembled panel paintings, as well as the remarkable drawings and intricate embroidery, do provide essential context. But painting in books is finally the surprising centerpiece of this magnificent exhibition.

Like the J. Paul Getty Museum in Malibu, which in a few eye-opening shows in recent years has been re-examining the role manuscript illumination played in European Renaissance art, the Met’s exhibition shines a light on a medium that has long been overlooked. Manuscript illumination is typically regarded as a form prominent in the Middle Ages, but one whose days were numbered by the Renaissance invention of movable type for the printing press. There’s truth to that view, but history is never quite so neat as that.

Painting in handmade books didn’t just stop, and illuminators didn’t simply find another line of work. The show demonstrates how numerous artists--Pacino di Bonaguida, the Master of the Dominican Effigies, the Master of the Codex of Saint George, Lorenzo Monaco, even Fra Angelico--painted in various mediums, including on wooden panels and on manuscript parchment. In the 14th and early-15th centuries, panel painting and manuscript illumination developed side by side.

In fact, manuscripts can sometimes offer a clearer indication of an artist’s work simply because a book can be closed: Colors don’t fade as centuries go by, and surfaces are protected in ways panel paintings aren’t. Manuscript illuminations frequently exude a startling freshness and clarity.

To be sure, many manuscripts have suffered at the hands of time. Countless books were disassembled into separate pages, especially in the 19th Century, in order to feed a hungry art market. Most of the illuminations in the Met exhibition suffered that fate. Furthermore, several are decorated letters of the alphabet that were actually cut from the page on which they were originally painted.

Panel paintings and altarpieces were also dismantled--or even sawed apart into pieces--to accommodate the market. One of the great pleasures of the show is that several panels and a variety of manuscript pages from dispersed books have been reunited here, for the first time since they were vandalized.

Don Silvestro dei Gherarducci was a Florentine monk who endowed panel and manuscript painting with a sense of narrative drama. Ten illuminations from a great choir book he painted for his monastery, Santa Maria degli Angeli, have been brought together from public collections in London; Cambridge, England; Geneva; Baltimore; Cleveland, and New York. Four of the five sections of the lower portion of an altarpiece by Fra Angelico, sawed apart at some unknown moment in history, are here reunited.

Perhaps the most remarkable assembly is the work of Lorenzo Monaco, an artist who has always seemed betwixt and between in the history of Italian art. In Lorenzo, something of the triumphant end of a medieval style merging into the full flowering of a Renaissance aesthetic can be seen.

Nearly one-quarter of the show--nine panelas, eight illuminations, eight drawings, one painting on glass and a collaboration with another artist--is devoted to Lorenzo, the largest gathering of his work ever. The variety of Lorenzo’s output (not to mention the presence of very rare drawings) suggests the workaday demands on successful artists of the period.

The simple, elegant weight of his most moving pictures underscores the likelihood that Lorenzo was indeed a teacher of Fra Angelico, who is the greatest artist in the show and among the greatest of the Renaissance. It’s a long way from a formal, highly stylized 14th-Century painting of the Madonna and Child by the Master of Saint Cecilia, with which the show opens, to the two optically precise, psychologically perceptive panels of the annunciation by Fra Angelico, with which it ends. But it is also a remarkable--even miraculous--trip certainly worth taking.

* “Painting and Illumination in Early Renaissance Florence,” Metropolitan Museum of Art, New York . Through Feb. 26. (212) 535-7710.