 Finally, in the development of set theory during the twentieth century it became clear that several of Dedekind’s results and procedures can be generalized in important ways. Perhaps most significantly, Zermelo and von Neumann succeeded in extending his analysis of mathematical induction and recursion to the higher infinite, thus expanding on, and establishing more firmly, Cantor’s theory of transfinite ordinals and cardinals. Looking back on all of these contributions, it is no wonder that Zermelo—who knew the relevant history well—considered the modern theory of sets as having been “created by Cantor and Dedekind” (quoted in Ferreirós 2016b).