Empiricism today implies the dispassionate scrutiny of facts. But Jessica Riskin finds that in the French Enlightenment, empiricism was inimately bound up with sensibility. In what she calls a sentimental empiricism, natural knowledge was taken to rest on a blend of experience and emotion. Riskin argues that sentimental empiricism brought together ideas and institutions, practice and politics. She shows, for instance, how the study of blindness, led by ideas about the mental and moral role of vision and by cataract surgeries, shaped the first school for the blind; how Benjamin Franklin's electrical physics, ascribing desires to nature, engaged French economic reformers; and how the question of the role of language in science and social life linked disputes over Antoine Lavoisier's new chemical names to the founding of France's modern system of civic education. Recasting the Age of Reason by stressing its conjunction with the Age of Sensibility, Riskin offers an entirely new perspective on the development of modern science and the history of the Enlightenment.