 Historically, both theses are directed broadly against the founders of modern logic and set theory such as Cantor, Peano, Frege, Russell, Zermelo, and Hilbert. On closer inspection, the historical situation is more complicated. With respect to Georg Cantor, for example, we must distinguish his work as a logical-set theoretical method useful in treating mathematical problems especially in the theory of functions on the one hand, and on the other hand, set theory as a tool for foundations or for considerations on infinite cardinality. Through Gösta Mittag-Leffler, Poincaré was familiar with Cantor’s work of the first type and uses it in his theory of Fuchsian functions in 1882 (Poincaré 1882: 1167), even having personal contact with Cantor (see Gray 1991: 22; Cantor 1991: 188; and Décaillot 2008: 281). However, Poincaré rejected the later foundational work of Cantor, saying that