André Marie Ampère was a French physicist and philosopher; his main achievement in physics was the foundation of electrodynamics. He correctly recognized that Hans Christian Ørsted's discovery, in 1819, of the effect of electric current on a magnetic needle was merely a special case of the general correlation of electricity in motion with the rise of a magnetic field. His explanation of magnetism in terms of molecular electric currents was a bold anticipation of one feature of the later electron theory.

Shortly after Ampère's death his Essai sur la philosophie des sciences appeared with a biographical note by Charles-Augustin Sainte-Beuve and a warm appraisal by Émile Littré. Its subtitle, Exposition analytique de toutes les connaissances humaines, indicated that the main topic was the classification of sciences, in which Ampère was...