Jan Stanisław Lewiński (1885-1930) was an economist and university lecturer. He left Poland as a child. He studied in Antwerp, London, Berlin and Brussels. During World War I, he worked at one of the institutes at the Cologne University. In the times of the Second Polish Republic, he was a lecturer at the Catholic University of Lublin and the Higher School of Commerce (later: SGH Warsaw School of Economics). He published not only in his native language, but also in German and English. He died in a tragic accident in Vilnius. Lewiński’s scientific interests were very broad. His works focused on theoretical issues, economic history and the history of economic thought. In this field, he appreciated the most the achievements of the physiocrats and classical economics. The author of Zasady ekonomii politycznej [Principles of Political Economy] tried to integrate the concepts of different economic schools. He indicated the need to take into account both theoretical factors and empirical aspects in the analysis of individual economic issues. For this reason, he perceived the dispute between the historical school and the classical school as barren. He assumed that all a priori assumptions must be confronted with the observation of reality, since a one-sided view would constitute a serious methodological error.