Today, a scientific explanation is not meant to ascribe agency to natural phenomena: we would not say a rock falls because it seeks the center of the earth. Even for living things, in the natural sciences and often in the social sciences, the same is true. A modern botanist would not say that plants pursue sunlight. This has not always been the case, nor, perhaps, was it inevitable. Since the seventeenth century, many thinkers have made agency, in various forms, central to science.

The Restless Clock examines the history of this principle, banning agency, in the life sciences. It also tells the story of dissenters embracing the opposite idea: that agency is essential to nature. The story begins with the automata of early modern Europe, as models for the new science of living things, and traces questions of science and agency through Descartes, Leibniz, Lamarck, and Darwin, among many others. Mechanist science, Jessica Riskin shows, had an associated theology: the argument from design, which found evidence for a designer in the mechanisms of nature. Rejecting such appeals to a supernatural God, the dissenters sought to naturalize agency rather than outsourcing it to a “divine engineer.” Their model cast living things not as passive but as active, self-making machines.

The conflict between passive- and active-mechanist approaches maintains a subterranean life in current science, shaping debates in fields such as evolutionary biology, cognitive science, and artificial intelligence. This history promises not only to inform such debates, but also our sense of the possibilities for what it means to engage in science—and even what it means to be alive.

Empiricism today implies the dispassionate scrutiny of facts. But Jessica Riskin finds that in the French Enlightenment, empiricism was intimately 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, practices 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.