Polish Émigré). Znaniecki became an expert on Polish migration, in 1914 authoring for the government a 500-page report, Wychodźtwo Sezonowe (Seasonal Migration). Work with Thomas A year earlier, in 1913, Znaniecki had met William I. Thomas, an American sociologist who had come to Poland in connection with his research on Polish immigrants in the United States. Thomas and Znaniecki had begun to collaborate, and soon Thomas invited Znaniecki to come to Chicago to continue work with him in the United States. In July 1914, just on the eve of World War I, Znaniecki left Poland to work with Thomas as a research assistant. From 1917 to 1919 Znaniecki also lectured in sociology at the University of Chicago. Their work culminated in co-authoring of The Polish Peasant in Europe and America (1918–1920), considered a sociology classic. It was his collaboration with Thomas that marked the transition in Znaniecki's career from philosopher to sociologist. Znaniecki stayed with Thomas in Chicago until mid-1919, when he moved to New York, following Thomas, who had lost his job at Chicago due to a spurious scandal. That year Znaniecki published a new book, still mostly philosophical rather than sociological, Cultural Reality. Published in English, it was a synthesis of his philosophical thought. In New York, Thomas and Znaniecki carried on research for the Carnegie Corporation on the process of immigrant Americanization. Znaniecki contributed to Thomas' book, Old World Traits Transplanted, and published an anonymous solicited article on that topic to the February 1920 Atlantic Monthly. Founding Polish sociology Poland had regained independence following World War I, in 1918. In 1919 Znaniecki contacted the newly founded Ministry of Religion and Education, offering to return to Poland if the Ministry could help him secure a chair at a Polish university. He proposed creating a novel Institute of Sociology, but bureaucracy and communication delays resulted in that idea being shelved, and he was offered a philosophy professorship at the newly organized Adam Mickiewicz University in Poznań. In 1920 Znaniecki returned to the newly established Second Polish Republic, where at Poznań University he soon became Poland's first chair in sociology. He accomplished this by renaming the department, originally "Third Philosophical Department", to "Department of Sociology and Cultural Philosophy", doing the same for his chair, and establishing a Sociological Seminary. That same year he also founded the Polish Institute of Sociology (Polski Instytut Socjologiczny), the fifth-oldest sociological institute in Europe. In