 Many of the quantities considered in 17th century calculus, such as Leibnizian infinitesimals, do not obey the Archimedean axiom. An infinitesimal can be added to itself any finite number of times but the outcome of that process will never be greater than any finite quantity, however small. A pervasive historiographical tradition has argued that with the elimination of infinitely small quantities from the calculus, non-Archimedean quantities were relegated to engineering practice for a long time. According to the standard account, it was only in the 1960s that infinitesimals came back when Abraham Robinson presented his theory of non-standard analysis, which has received a lot of attention from philosophers and mathematicians (see section  3.4.2).  Robinson’s theory gave a legitimate mathematical status to infinitely small and infinitely large quantities in the reconstruction of the infinitesimal calculus, now developed accordingly to rigorous model-theoretic techniques. For a long time, Robinson’s work was hailed as the first successful effort to develop a system of non-Archimedean quantities. But Philip Ehrlich, in a series of fundamental papers (including 1994, 2012), has argued that this widespread perception needs serious questioning. Indeed, he has shown convincingly that interest in non-Archimedean mathematics emerged in the 1870s and continued to grow in the hands of mathematicians such as Veronese, du Bois-Reymond, Levi-Civita, Hahn, Stolz, Hardy, and others.