The author applies the general categories of Marxist philosophy, time and apace, to the concrete problems of psychological and social phenomena. The material bearer of mental ripening is the individual, whose mental maturity is the result of the dialectical operation of the activity of a subject with certain dispositions in his life’s field. The individual’s life’s field consists of three components: biological, mental and social fields, which form a structured unity of the conditions for the individual’s life. The parents’ education is an important element in the mental and social fields. A group of 2,100 children aged between ten and fifteen were tested by the KVIT test and the author found the following relations: The rational abilities of children whose father had a higher education developed rapidly between the ages of twelve and fourteen, after that the development slows down. The beginning of the dynamic development of children whose father had an elementary education comes la ter. The rapid development of mental abilities starts at the age of thirteen and this trend still continues a t the age of fifteen. On the basis of an analysis of the course of mental ripening of children whose father had elementary education and those whose father had higher education the author comes to the conclusion that there exists mental time as a co-ordinate of the mental ripening process. Thus mental ripening, whose material bearer is the individual, is taking place in a specific space — the mental field and the mental time inherent in it.