If there is any subject which, more than all others, divides opinion and provokes endless controversy among librarians and scholars, it is the proper classification of books. From the beginning of literature this has been a well-nigh insoluble problem. Treatise after treatise has been written upon it, system has been piled upon system, learned men have theorised and wrangled about it all their lives, and successive generations have dropped into their graves, leaving the vexed question as unsettled as ever. Every now and then a body of _savans_ or a convention of librarians wrestles with it, and perhaps votes upon it, "And by decision more embroils the fray" since the dissatisfied minority, nearly as numerous and quite as obstinate as the majority, always refuses to be bound by it. No sooner does some sapient librarian, with the sublime confidence of conviction, get his classification house of cards constructed to his mind, and stands rapt in admiration before it, when there comes along some wise man of the east, and demolishes the fair edifice at a blow, while the architect stands by with a melancholy smile, and sees all his household gods lying shivered around him. Meanwhile, systems of classification keep on growing, until, instead of the thirty-two systems so elaborately described in Edwards's Memoirs of Libraries, we have almost as many as there are libraries, if the endless modifications of them are taken into account. In fact, one begins to realise that the schemes for the classification of knowledge are becoming so numerous, that a classification of the systems themselves has fairly become a desideratum. The youthful neophyte, who is struggling after an education in library science, and thinks perhaps that it is or should be an exact science, is bewildered by the multitude of counsellors, gets a head-ache over their conflicting systems, and adds to it a heart-ache, perhaps, over the animosities and sarcasms which divide the warring schools of opinion. Perhaps there would be less trouble about classification, if the system-mongers would consent to admit at the outset that no infallible system is possible, and would endeavor, amid all their other learning, to learn a little of the saving grace of modesty. A writer upon this subject has well observed that there is no man who can work out a scheme of classification that will satisfy permanently even himself. Much less should he expect that others, all having their favorite ideas and systems, should be satisfied with his. As there is no royal road to learning, so there can be none to classification; and we democratic republicans, who stand upon the threshold of the twentieth century, may rest satisfied that in the Republic of Letters no autocrat can be allowed.