Beauvoir expressed a disappointment with politics after World War II, and she addressed the importance of mass action and relations between political party leaders and their followers and colleagues. She applied Jean-Paul Sartre’s (1905–1980) existential philosophy to politics, criticizing “the spirit of seriousness” that characterized those who did not take responsibility for their political actions as free individuals. Although Sartre had never written on ethics, she thought that ethical positions and decisions would arise from compelling passions and circumstances. The best interpretation of Beauvoir’s The Ethics of Ambiguity (1947) is not that ethics is itself ambiguous but that ethics is somewhat arbitrary from an existentialist perspective.