In the work there is an original interpretation of religious mentality of medieval people. The author introduces a new concept of ‘religious fund’, under which he meant a typical reaction of a man of a certain group, or as a complex of religious habits in the sphere of thought, emotions, and will. He considered, that it was impossible to search for the religious fund in Scholasticism. The book by K. anticipated a later work on the medieval mentality. The author set a question of the bearer of the ‘religious fund’ – or ‘a man of the epoch’, the concept existing for any certain cultural period. He also used such concept as ‘an average man’. Insisting at the principal limits of the individualistic-pantheistic mentality, K. drew a difference between individualism and personalism. The later one allowed to escape a characteristic Renaissance contradiction between the universalist intention of pantheism and individualistic atomism. Analyzing the works by Augustine the Hippo, he made an accent at the establishing the idea of personality, individuality of a man. The author did not separate himself from the religious tradition which was the object of his research. Particularly, the initial impulse was the concept that the religious mentality is an integral part of the human nature.