LIBRARIES ARE AGAIN being besieged, although not yet being burned. Public and university libraries -- the latter include many of the great research libraries -- are critically short of money. School and public libraries are being plagued by the efforts of a virulent minority to censor them. Yet the majority seem to manage only a yawn at "another 'Save the Libraries' plea."

Libraries perform many useful services. One of the programs now offered by many libraries -- and threatened by cuts -- teaches illiterate and foreign-born people how to read. Many who take advantage of these programs are unemployed or underemployed. As the librarian of the Queens Borough Library in New York has said: "For them, this is the road toward filling out a job application or reading a want ad."

But the case for public libraries does not rest only on utilitarian arguments. We must have a feel for what they are. A mother who is actively campaigning for the proposed new library in western Prince William County told a Washington Post reporter: "My little boy just sits and cries and cries because I can't take him to the library when it starts to snow. It's too far and the roads are too bad." Those tears, appropriately, speak volumes.

I sympathize with the boy from my own childhood. I do not know what I would have done without a library only a mile away. During my school holidays I arrived there as its doors opened in the morning. One summer a chain grocer's on the way was giving away free samples of a new import from America: I stopped on the way both to and from the library to eat my first waffles as they dripped with golden syrup.

Sometimes I finished the book which I had taken out in the morning before the library had closed in the evening. I took it back to exchange it for another, to be told that one could not return a book on the same day. This was one of my first encounters with bureaucracy: not even the cunning of a schoolboy could get around it. I took to filching the library cards of my six brothers and sisters.

Libraries are more than the number of individual books in them. It is that they are all gathered together, cheek by jowl, that is so inviting and endlessly intriguing. That there should be so many books -- yes -- but also so many worlds they can open. You have to be patient with a small child in a library. Even if he is choosing only between picture books, he is choosing between lands and continents.

Books are living things. Libraries are living places. Nat Hentoff recently recalled that he spent his evenings as a boy in the Brooklyn Public Library. When he added that he was "far from the only kid there," Norman Mailer responded: "I was one of those kids." That tells a lot. One knows why other kids are at the movies or a ballpark -- but what is that kid over there doing and reading in the library?

To read of a private library that has been dispersed is like reading of something living that has been dismembered. Cicero lost most of his precious library when he was driven into exile, yet he seems to have recovered some of the books, for he wrote to his friend Atticus that a slave named "Tyrannion has made a wonderfully good arrangement of my books, the remains of which are better than I had expected."

He borrowed two other library slaves from Atticus to help "as gluers and in other subordinate work," and wrote to Atticus later that they had done their work well: "Your men have beautified my library by making up the books and appending title slips. . . . Since Tyrannion has arranged my books for me, my house seems to have had a soul added to it." Every lover of libraries will respond to that.

One Sunday evening a few years ago I called my friend William A. McPherson to ask if I might drop around. He said that he was rearranging his books. Far from this being a deterrence, I was all the more eager to go. Rearranging one's library is a physical as well as an intellectual labor. I cannot say that I contributed much physically. I sat in an armchair, and directed the operation, sipping his scotch as a reward.

The library of the editor of Book World, as he then was, is interesting to a mere reviewer for it. "Now I see," I exclaimed at one moment, "why I never get the hardback copies of the books I have reviewed from the galley proofs." Nevertheless I continued with my advice and his scotch, devising categories for books with no obvious place. In his own library, I was Cicero, he the slave Tyrannion.

The problems that arise in arranging one's own books remind one of the importance of cataloguing. Anyone who has studied the Dewey decimal system, or the eccentric and complex system used by the Library of Congress, must realize that cataloguing is genuinely an intellectual exercise. Both classifications for every book now published are given on the reverse of its title page.

What cataloguing involves is a series of decisions about the borderlines between different branches of knowledge. Should a book be entered under "Psychology" and, if so, under what branch of "Psychology"? It is not all that many years since "Psychology" freed itself at Harvard from "Philosophy," and a librarian of stern mind and intellectual discipline might catalogue it there again. It would be perverse of him but interesting.

Playing Cicero in McPherson's home, I found him a rebellious Tyrannion, with some slack and American notions. By the end he showed an inclination to throw every book which could not easily be classified into a pile which he indiscriminately called "Travel." I suppose that to an American everything done, said or written beyond these shores does seem like "Travel."

We scarcely had so awesome a task as that which faces the Librarian of congress, but what made the occasion so memorable was that, as we considered where a book should be put, we were discussing what the book was really about. Merely rearranging the books in one's own home is a reflection of the infinite worlds that await exploration in any library. What is more, the worlds overlap. A child with his picture book knows that.

Columbus found some of his inspiration in the books that he read. But it was his fascinating and scholarly son Ferdinand who collected a large and splendid library of more than 15,000 volumes. That is an extraordinary number of books for the beginning of the 16th century. At his death his library went to the cathedral chapter of Seville, at whose hands "it suffered shameful neglect and dilapidation."

Among the 2,000 volumes that remain is his copy of Seneca's "Medea," in which Seneca prophesied that "An age will come after many years when the Ocean will loose the chains of things, and . . . disclose new worlds." In the margin against this prophecy, Ferdinand wrote the tremendous words: "This prophecy was fulfilled by my father . . . the Admiral in the year 1492." Not many books contain such a triple reminder -- Seneca's, Columbus', Ferdinand's -- of the worlds within them waiting to be explored.

Yet in the small space of any library are those worlds, and a small boy cries if he is kept from them. At a meeting held recently to raise funds for the Brooklyn Public Library, writers as different as Irwin Shaw, Frederick Pohl and Isaac Bashevis Singer testified to the use which they had made of libraries as boys -- and still as adults. "When I come to a new place," said Singer, "my first question is, 'Is there a library here?' "

One can, of course, carry the addiction too far. Sir Thomas Phillipps, born in 1792 and died in 1872, collected a vast library. "I want to have one Copy of every Book in the World!!!!!", he once declared. One of his friends noticed that Phillipps' house was sinking into the ground under the weight, and his wife understandably wrote: "Oh, if you would not set your heart so much on your books, . . . how thankful I should be!"

His fortunate descendants are still, bit by bit, auctioning off the library. More than one generation has made tidy sums out of the collection. One wishes that Phillipps had had the foresight of a J.P. Morgan or a Henry E. Huntington, to make provisions for keeping his library together. The Huntington Library in Pasadena is now a national treasure.

Among a heap of wastepaper which Phillipps kept -- he kept everything -- was found the lost half of the original manuscript of Caxton's Ovid. In a single volume, again, ages and worlds are joined. But the whole point of such stories is that from a small boy picking out a picture book, to a schoolboy picking up waffles on the way to the library, to the student trying to learn or merely wishing to read, to the careful scholar and the ordinary adult reader, there is nowhere else, not a movie or a docudrama, that can so transport one to worlds upon worlds upon worlds all in one room or building, as a library and its stacks.