WHILE THE FOLGER Shakespeare Library is busy celebrating the 415th anniversary of Shakespeare's birth today, there ought to be some celebration for the celebrants. There is no library, no cultural institution in the city more appealing than the Folger, none run with a greater sense that the best place for antiquity is with the living. Nothing is forbidding about the library, in spite of its size and stature. Neither does it try to twist itself into a carnival in order to suit some imaginary popular taste. Thanks to the spirited, sensible direction of O. B. Hardison Jr., the library has become a model monument in a town of monuments, a place where the honoree thrives.

Mr. Hardison and others of Shakespeare's friends are celebrating the bard's birthday today as if he were around to blow out the candles. That is probably exactly as Henry Clay Folger and Emily Jordan Folger would have wished it. Mr. Folger and Shakespeare first met 100 years ago, in the spring of 1879 at Amherst College, in Folger's senior year. He spent a whole 25 cents to listen to a lecture by the aging Emerson, who said that Shakepeare "taught us that the little world of the heart is vaster, deeper and richer than the spaces of astronomy." Mr. Folger spent a good deal more than a quarter on Shakespeare thereafter. To start his collection in 1885, he bought as a gift for his bride a facsimile copy of the 1923 First Folio edition of Shakespeare's works, for $1.25 - which showed he had an eye.

Mr. Folger, who worked his way to the chairmanship of the board of Standard Oil, was not rich as millionaires go. He spent most of his fortune on his collection, and when he had bought the land and building for the Folger library, and had no more money for books, he gave IOUs to his wife so he could go on collecting. The current library collection includes, beside Shakespeare, Renaissance atlases, histories of science, the letters of John Donne, original editions of Luther, Calvin and Erasmus - a treasury for scholars. In its public functions, the library has become a treasury in its own right, with its poetry readings, films, lectures and the remarkable work of the Fogler Theatre Group, whose plays, ancient and modern, are performed in an Elizabethan theater without a bad seat in the house.

Like all privately endowed cultural insitutions, the Folger has had to go through hoops quite often, and invent occassions to raise money and keep itself afloat. For today, however, it enjoys an unsullied moment in honoring the man who, as Robert Browning said, "was of us."