 Once the continuum had been provided with a set-theoretic foundation, the use of the infinitesimal in mathematical analysis was largely abandoned. And so the situation remained for a number of years. The first signs of a revival of the infinitesimal approach to analysis surfaced in 1958 with a paper by C. Schmieden and D. Laugwitz. But the major breakthrough came in 1960 when it occurred to the mathematical logician Abraham Robinson (1918–1974) that 