Brunschvicg Léon (1869–1944), French philosopher, an influential professor at the Sorbonne and the École Normale Supérieure of Paris, and a founder of the Revue de Métaphysique et de Morale (1893) and the Société Française de Philosophie (1901). In 1940 he was forced by the Nazis to leave Paris and sought refuge in the nonoccupied zone, where he died. A monistic idealist, Brunschvicg unfolded a philosophy of mind (Introduction to the Life of the Mind, 1900). His epistemology highlights judgment. Thinking is judging and judging is acting. He defined philosophy as ‘the mind’s methodical self-reflection.’ Philosophy investigates man’s growing self-understanding. The mind’s recesses, or metaphysical truth, are accessible through analysis of the mind’s timely manifestations. His major works therefore describe the progress of science as progress of consciousness: The Stages of Mathematical Philosophy (1912), Human Experience and Physical Causality (1922), The Progress of Conscience in Western Philosophy (1927), and Ages of Intelligence (1934). An heir of Renouvier, Cournot, and Revaisson, Brunschvicg advocated a moral and spiritual conception of science and attempted to reconcile idealism and positivism. J.-L.S.