Answer:
Thomas De Quincey, "The Literature of Knowlege and the Literature of Power" (First Published in the North British Review, August, 1848, as part of a critical essay on Alexander Pope)
Every great classic in our native language should from time to time be reviewed anew; and especially if he belongs in any considerable extent to that section of the literature which connects itself with manners, and if his reputation originally, or his style of composition, is likely to have been much influenced by the transient fashions of his own age. The withdrawal, for instance, from a dramatic poet, or a satirist, of any false luster which he has owed to his momentary connection with what we may call the personalities of a fleeting generation, or of any undue shelter to his errors which may have gathered round them from political bias, or from intellectual infirmities amongst his partisans, will sometimes seriously modify, after a century or so, the fairest original appreciation of a fine writer. A window composed of Claude Lorraine glasses spreads over the landscape outside a disturbing effect, which not the most practiced eye can evade. The eidola theatri ["idols of the theater," one of Francis Bacon's Idols of the Mind — ed.] affect us all. No man escapes the contagion from his contemporary bystanders.
As books multiply to an unmanageable excess, selection becomes more and more a necessity for readers, and the power of selection more and more a desperate problem for the busy part of readers. The possibility of selecting wisely is becoming continually more hopeless as the necessity for selection is becoming continually more pressing. Exactly as the growing weight of books overlays and stifles the power of comparison, pari passu is the call for comparison the more clamorous; and thus arises a duty correspondingly more urgent of searching and revising until everything spurious has been weeded out from amongst the Flora of our highest literature, and until the waste of time for those who have so little at their command is reduced to a minimum. For, where the good cannot be read in its twentieth part, the more requisite it is that no part of the bad should steal an hour of the available time; and it is not to be endured that people without a minute to spare should be obliged first of all to read a book before they can ascertain whether in fact it is worth reading. The public cannot read by proxy as regards the good which it is to appropriate, but it can as regards the poison which it is to escape. And thus, as literature expands, becoming continually more of a household necessity, the duty resting upon critics (who are the vicarious readers for the public) becomes continually more urgent — of reviewing all works that may be supposed to have benefited too much or too indiscriminately by the superstition of a name. The praegustatores ["pre-tasters," ie those whose obligation was to taste a Roman emperor's food to determine its fitness for eating — ed.] should have tasted of every cup, and reported its quality, before the public call for it; and, above all, they should have done this in all cases of the higher literature — that is, of literature properly so called.
What is it that we mean by literature? Popularly, and amongst the thoughtless, it is held to include everything that is printed in a book. Little logic is required to disturb that definition. The most thoughtless person is easily made aware that in the idea of literature one essential element is some relation to a general and common interest of man — so that what applies only to a local, or professional, or merely personal interest, even though presenting itself in the shape of a book, will not belong to literature. So far the definition is easily narrowed; and it is as easily expanded. For not only is much that takes a station in books not literature; but inversely, much that really is literature never reaches a station in books. The weekly sermons of Christendom, that vast pulpit literature which acts so extensively upon the popular mind — to warn, to uphold, to renew, to comfort, to alarm — does not attain the sanctuary of libraries in the ten-thousandth part of its extent. The drama again — as, for instance, the finest of Shakespeare's plays in England, and all leading Athenian plays in the noontide of the Attic stage — operated as a literature on the public mind, and were (according to the strictest letter of that term) published through the audiences that witnessed1 their representation some time before they were published as things to be read; and they were published in this scenical mode of publication with much more effect than they could have had as books during ages of costly copying or of costly printing.
I hope it's helpful!