What is “geometric algebra”, and what has it been in historiography? Jens Høyrup Roskilde University Section for Philosophy and Science Studies
[email protected] http://ruc.dk/~jensh Contribution to the session Histoire de l’historiographie de l’algèbre Séminaire Histoire et Philosophie des Mathématiques CNRS, SPHERE, & projet ERC SAW Université Paris Diderot, 11 janvier 2016 PREPRINT 15 January 2016 Abstract Following the lead of Hans Georg Zeuthen (not that of Tannery, as often claimed), many historians of mathematics since the outgoing nineteenth century have referred to “geometric algebra” as a constituent of ancient Greek theoretical geometry. In the 1930s, Otto Neugebauer added that this geometric algebra was indeed a translation of a Babylonian numerical algebra, necessitated by the discovery of irrational ratios. Then, beginning in 1969, the notion was attacked, first by Árpád Szabó, Michael Mahoney and Sabetai Unguru. In particular the views of the latter have since been accepted as the “new orthodoxy”. As analysis of the writings of the actors involved shows, these have rarely read each other’s works with much care. That already holds for many of those who have claimed inspiration from Zeuthen, but those who have criticized the idea have felt even less obliged to show that they knew what they spoke about. The paper deals with this relationship between the participants in the debate. It is not intended to discuss who is right when it comes to analysis of the historical material. Contents Before “geometric algebra” ................................... 1 When did it start? Tannery or Zeuthen? ......................... 4 Further on, first phase: Thomas Heath and Moritz Cantor ..........