A scientific paradox according to that authority of scientist is the best of all determined by that is well-known, as far as he put on the brakes development of science in the area. So, all modern world psychology of child's thinking is literally blocked by the ideas of the prominent Swiss psychologist Jean Пиаже (1886-1980), one of main works of that and presented in this book. Great number of subsequent researches touch clarification only empiric facts, but practically there are not works criticizing his theories. Even modern psychologists do not succeed to break forth outside the system worked out to them. Пиаже laid new ways in psychological science, first translating the traditional questions of theory of cognition in the area of child's psychology and experimentally proved them, creating new methods, opening the unknown to him laws of heartfelt life of child.Hired, first going out in Russian language as early as 1932, and till today remains actual, determining the base sources of scientific cognition of child's psychology. She is the result of long-term researches of such psychical functions in child's age, as thinking and speech, and brightly characterizes a transition from realistic perception to actual one, stage-by-stage, from the внеречевого аутистического thinking of baby and further on the measure of maturing child, through egocentric speech and egocentric thinking to the socialized speech and logical thinking of teenager.The anonymous translation published in 1932 by the State educational-pedagogical publishing house is fixed in basis of edition.