Data Arithmetic, Ratios and Mechanical Reasoning in the 17th and 18th Centuries

What was data work in the seventeenth century? It was in commercial transactions that the most massive amount of digital information was processed. Reconstructing the know-how of this period leads us to two authors who have long been the models for apprentice calculators: Euclid and Fibonacci. During the Renaissance and the early modern period, the lessons learned from both stumbled over the concept of ratio. A presupposition was thus formed that a ratio was conceived as sealed. Establishing this usage and conception has several consequences. One can better understand the importance then taken by approximative and the mechanistic reasoning. And we can put an end to two historiographical legends: no, the beginning of the calculation of probabilities owes nothing to maritime insurance; no, similarly, the calculation of the French population around 1800 was not solved by Laplace’s sampling methods.