That's not quite true. We can do several things. One is to accept the limitations of the much-derided filters and use them anyway. The government argues, convincingly, that when libraries use the filters, ''They are simply declining to put on their computer screens the same content they have traditionally excluded from their bookshelves.'' A second possibility is the so-called ''Boston solution,'' adopted several years ago in Copley Square by the nation's oldest public library.