In rhetoric, an orator needs both a large vocabulary and a stock of commonplaces and arguments. Erasmus put them together in his De duplici copia verborum ac rerum . In this sixth volume of the first Ordo of the Amsterdam edition of the Latin texts of Erasmus, Betty Knott has edited the Latin text and added an English introduction and commentary, providing philological and historical information which helps the reader to understand the text and identify its sources.