Fibonacci – Protagonist or Witness? Who Taught Catholic Christian Europe about Mediterranean Commercial Arithmetic?

Abstract

Leonardo Fibonacci (ca. 1170 -after 1240 during his boyhood went to Bejaïa, learned about the Hindu-Arabic numerals there, and continued to collect information about their use during travels to the Arabic world. He then wrote the Liber abbaci, which with half a century's delay inspired the creation of Italian abbacus mathematics, later adopted in Catalonia, Provence, Germany etc. HinduArabic numerals, and Arabic mathematics, was thus transmitted through a narrow and unique gate. This piece of conventional wisdom is well known -too well known to be true, indeed. There is no doubt, of course, that Fibonacci learned about Arabic (and Byzantine) commercial arithmetic, and that he presented it in his book. He is thus a witness (with a degree of reliability which has to be determined) of the commercial mathematics thriving in the commercially developed parts of the Mediterranean world. However, much evidence -presented both in his own book, in later Italian abbacus books and in similar writings from the Iberian and the Provençal regions -shows that the Liber abbaci did not play a central role in the later adoption. Romance abbacus culture came about in a broad process of interaction with Arabic non-scholarly traditions, at least until ca. 1350 within an open space, apparently concentrated around the Iberian region.