On the intuitive set theory and its formalization

The present paper investigates the reasons of occurrence of known paradoxes in the intuitive set theory. We have proved that the process of formation of sets is non-finishing, and the reason of occurrence of paradoxes consists in representation of formation of sets as a finishing process (in other words, the reason of occurrence of paradoxes is the identification of concepts of a set and a class). The possibility of full formalization of the intuitive set theory is suspected.