"On the Knocking at the Gate in Macbeth" is an essay in Shakespearean criticism by the English author Thomas De Quincey, first published in the October 1823 edition of The London Magazine. It is No. II in his ongoing series "Notes from the Pocket-Book of a Late Opium Eater" which are signed, "X.Y.Z.". The first part of this dispatch is "Malthus", a much longer essay debunking the economist's theory of overpopulation.: 349, 356  Source: Wikipedia (en)