Abstract

A calculating prodigy, or mental calculator, is someone who can mentally perform mathematical operations involving very large numbers or very fast mental calculations. From the nineteenth to the beginning of the twentieth century, this phenomenon met with considerable interest, and several calculating prodigies became famous enough for us to trace their careers. They found themselves at the crossroads of three worlds: the world of entertainment, where their skill at juggling numbers was admired; the world of the brain and psyche, where their peculiarities were explained and used to better understand how the brain functions; and finally, the world of mathematics, where the reproducibility of their methods and their potential as future scientists were of interest. By examining the commonalities in their trajectories, this article explores the images and practices behind the development of numeracy, at the intersection of reasoning and calculation, in nineteenth- and early twentieth-century Western societies.