The collection comprises the following series: Biographical material; Bibliographies; Articles, addresses, essays; MSS drafts and synopses for proposed publications; Drafts and notes for Maxims; Working paper and notes; and Corresondence. Pledge is best know for his book 'Science since 1500,' London: H.M.S.O., 1939, 2nd ed. 1966. Some of the notes in the collection were probably assembled for this book; but it is clear that throughout his life Pledge had been accumulating material for an ambitious project which would be both an encyclopedia and world history and an interpretation and synthesis of knowledge. Work on this became his main concern from ca. 1940 until his death, as is shown by the dating of his notes. His wide range of reading and thinking produced copious notes, which he re-arranged and reallocated according to an increasingly elaborate system, while the many plans and charts he devised show the scale of his intention and the problems he encountered.