The article deals with Russell’s and Florenky’s theories in epistemology and philosophy of mathematics. Both of philosophers are the participants of realistic view. Both of philosophers put mathematical logic as the basis of philosophy. The main concepts of the article are: proposition, description, number, set theory, universals, certainty, etc. Russell and Florensky make the opposite resolutions from the philosophy of mathematics. Florensky evolves to the religious mystics and the aesthetics. Russell moves to positivism and philosophy of science. Russell and Florensky are the antipodes in main and principal positions, but there is one common thing: they are creators of philosophical systems with extremely large scope.