The essay deals with Margit Cassel (1897–1994) who was the first Swedish woman ever to receive a doctoral degree in economics from the University of Lund in December 1924. Her ‘opponent’ was Bertil Ohlin who shortly before had been appointed professor at the University of Copenhagen. Margit Cassel’s PhD thesis was concerned with collective wants and collective goods that had become a major issue in public finance after World War I. The core is about the indivisibility of collective goods as a reason for a public sector economy. Margit Cassel distinguishes between passive demand and active demand for public goods, which should be paid for directly by the person enjoying it and not by tax money. In her foundational treatise on the public sector Cassel made a lasting contribution to the economics of the public sector. Whereas this was recognized in the contemporary German literature, her contribution undeservedly fell into oblivion. Margit Cassel Wohlin became a mother of four children in five years and was then divorced by her husband. She left Academia.