At first critics classified authors as Ancients, that is to say, Greek and Latin authors, and Moderns, that is to say, every post-Classical Author. Then they classified them by eras, the Augustans, the Victorians, etc., and now they classify them by decades, the writers of the '30's, '40's, etc. Very soon, it seems, they will be labeling authors, like automobiles, by the year.
