Jules Lachelier, the French idealist, was born at Fontainebleau and studied at the École Normale Supérieure in Paris. He received his docteur ès lettres in 1871 and held various professorial and administrative positions in the French educational system until his retirement from the post of inspecteur général in 1900. Lachelier joined with his teacher Jean Gaspard Félix Ravaisson-Mollien in founding the neospiritualist movement in French philosophy, a movement opposed to what seemed to be the naive acceptance of science and the scientific attitude in all phases of life. Among those who have acknowledged Lachelier's influence are Émile Boutroux, Victor Brochard, Jules Lagneau, and Henri Bergson.

Lachelier advanced a number of skeptical arguments that tend to reduce objects to phenomena, phenomena to sensations, and, more generally, to resolve the external world into thought. Nevertheless, he retained the conviction that we live in a...