The author underlines the value of P. P. Blonsky's approach to the problem of knowledge mastering. It is based on dialectical interrelation of perception, memory, thinking, speech. The development of each to these components has its own importance for schoolchildren's knowledge mastering on different stages of their age-specific development. Special attention is paid to P. P. Blonsky's views on thinking's role in better knowledge mastering, perception, memory (memorizing and remembering in particular). P. P. Blonsky's ideas concerning self-control development in knowledge mastering process are reviewed.