French historian and philosopher, who showed considerable originality in his development of the general principles of physical theory. He introduced a new atomism into the mechanistic system of René Descartes by linking unity and substantiality; matter is homogeneous but contains a multiplicity of bodies each of which is an individual substance. His works include Le Discernement du corps et de l'âme (1666; “The Differentiation of the Body and the Soul”) and Lettre à un savant religieux de la Comp. de Jésus (1668), on animal magnetism.