The article precedes the publication of an archival manuscript by Anatoly Rosenblum (1900-1938), a representative of the Kharkov Psychological School, a colleague and close friend of A.N. Leontiev, a bright and original researcher, tragically died in the period of Stalin’s repressions. The aim of the article is a historical and theoretical analysis of the results of empirical research by A.I. Rosenblum in the context of other developments of the Kharkov School in 1932-1935, as well as assessment of their contribution to the formation of the activity approach in psychology. The methodological basis of this study is a three-faceted approach to the analysis of the history of science proposed by M.G. Yaroshevsky. In accordance with it, some details of A.I. Rosenblum’s biography are expounded in the sociocultural context of his epoch, with using the personal letters stored in A.N. Leontiev’s family archive. This is followed by a historical and psychological analysis of the theoretical foundations and empirical results of A.I. Rosenblum’s research in comparison with the works of other Kharkov psychologists (P.Ya. Galperin, A.V. Zaporozhets, P.I. Zinchenko, G.D. Lukov, etc.). As is demonstrated in the article, A.I. Rosenblum has managed to uncover a complex dialectic of the relationship between “image” and “process” at different stages of children’s craftsmanship activity (modelling a chain of rings out of plasticine). He showed how exactly the developing “process” (a system of practical operations necessary for making an object) ultimately leads to a qualitative change in the original image of this object in children’s minds. It is emphasized that A.I. Rosenblum made thereby a significant contribution to the resolution of the problem of the correlation between “image” and “process” in the human psyche. This problem was posed by L.S. Vygotsky, and A.I. Rosenblum solved it from the standpoint of the activity approach. It was concluded that his research results confirmed very convincingly the central statement of the theory of activity: we always acquire the knowledge of the world through activity, and not as a direct reflection of the objective world. This statement sharply contradicted the “theory of reflection” canonized in the USSR, but it corresponded to the principles of cultural activity psychology, founded by L.S. Vygotsky. The author of the article considers this as the evidence of the inner unity of cultural activity psychology, despite all the differences of L.S. Vygotsky’s and A.N. Leontiev’s scientific programs at different times.