 In 19th century German-speaking areas, there were some intellectual tendencies that promoted the acceptance of the actual infinite (e.g., a revival of Leibniz’s thought). In spite of Gauss’s warning that the infinite can only be a manner of speaking, some minor figures and three major ones (Bolzano, Riemann, Dedekind) preceded Cantor in fully accepting the actual infinite in mathematics. Those three authors were active in promoting a set-theoretic formulation of mathematical ideas, with Dedekind’s contribution in a good number of classic writings (1871, 1872, 1876/77, 1888) being of central importance.