Léon Brunschvicg, the French idealist philosopher, was born in Paris and educated at the Lycée Condorcet, where he won awards in science as well as in classics and philosophy. He received both the licence ès lettres and the licence ès sciences from l'École Normale Supérieure in 1891. During the following nine years he taught philosophy at lycées in Lorient, Tours, and Rouen. His doctoral thesis, La modalité du jugement, was presented to the Sorbonne in 1897, and published in Paris the same year. In 1900 he returned to Paris to teach at his old lycée, later moving to the Lycée Henri IV and l'École Normale de Sèvres. In 1909 he was named professor of general philosophy at the Sorbonne. Except for the period 1914–1918, when he served in the armed forces auxiliary and as...