Experimental social psychologists often claim Kurt Lewin as the founder of modern social psychology. This chapter looks at the influences of his teacher, the philosopher Ernst Cassirer, and his friendship with Karl Korsch, the Marxist philosopher. Lewin rejected conventional laboratory experiments as being unscientific, and he developed a form of experiment to examine concrete cases. Lewin’s famous study of democratic and authoritarian leadership shows both the strengths and weaknesses of his new psychology. The strength was the richness of its examples, and the weakness was his physics-based theory for understanding those examples. Focussing on one example, it is argued that Lewin would have gained a richer understanding of what was happening if he had used a bit more Korsch and Cassirer - especially Cassirer’s ideas on psychology and his views on description as explanation. Lewin is praised for his humane, dedicated vision and for being an example to follow.