A core principle of modern science holds that a scientific explanation must not attribute will or agency to natural phenomena. "The Restless Clock" examines the origins and history of this, in particular as it applies to the science of living things. This is also the story of a tradition of radicals--dissenters who embraced the opposite view, that agency is an essential and ineradicable part of nature. Beginning with the church and courtly automata of early modern Europe, Jessica Riskin guides us through our thinking about the extent to which animals might be understood as mere machines. We encounter fantastic robots and cyborgs as well as a cast of scientific and philosophical luminaries, including Descartes and Leibnitz, Lamarck and Darwin, whose ideas gain new relevance in Riskin's hands. The book ends with a riveting discussion of how the dialectic continues in genetics, epigenetics, and evolutionary biology, where work continues to naturalize different forms of agency. "The Restless Clock "reveals the deeply buried roots of current debates in artificial intelligence, cognitive science, and evolutionary biology.