The widespread assessment of the early period of Semyon L. Frank’s work as being influenced by German Neo-Kantianism is in need of a critical scrutiny. There are several reasons why the Russian philosopher’s interest in Neo-Kantianism merits a closer look. First, two systemic theories belonging to different trends exerted a decisive influence on Russian philosophy in the late nineteenth and early twentieth centuries: German Neo-Kantianism and Vladimir Solovyov’s school of all-unity. Second, Frank himself and the German Neo-Kantians considered Nicholas of (...) Cusa to be one of their forerunners and pointed out the importance of his mathematical ideas for their mathematical studies. Thirdly and lastly, Frank paid particular attention, especially in his formative period as a philosopher, to the leading trend in the early twentieth century, namely German Neo-Kantianism, which led some students of his work to believe that German Neo-Kantianism played the decisive role in Frank’s abandonment of Marxism in favour of religious ontology. Frank’s fundamental disagreement with German Neo-Kantianism was expressed in his work The Object of Knowledge in which he criticised the Neo-Kantian concepts of number and time. Although Frank rightly points out the one-sidedness of the Neo-Kantian definition of number, most notably in the works of the Marburg philosopher Paul Natorp, on the whole his criticism of the Neo-Kantian concept of number and time as being different from his own is not entirely convincing. In my opinion, Frank’s attempt to explain the abstract concept of number through a still more abstract concept of all-unity was not crowned with success because he ignored the experience of Christian theology and the Trinity dogma as well as the profound thoughts of the Rev. Pavel Florensky on this topic. (shrink)