The Swedish philosopher Hägerström, who was professor in Uppsala during the first quarter of the present century, devoted much attention to the philosophical and psychological analysis of moral and legal phenomena. Hägersträm is a difficult writer. He had steeped himself in the works of German philosophers and philosophical jurists, and his professional prose-style both in German and in Swedish had been infected by them so that it resembles glue thickened with sawdust. But he enjoys a very high reputation in his own and adjacent countries, and it seems to me that this is well deserved. I think, therefore, that it may be interesting and useful to try to provide English philosophers with an outline in my own words of Hägerström's doctrines, as I understand them, about the topic named in the title of this paper.