 In the Observations, Hartley offers a conceptually novel treatment of physical action—a topic largely absent from other treatises, or inquiries, devoted to “human nature” or “human understanding.” Even in James Mill’s Analysis of the Phenomena of the Human Mind, a work with an acknowledged debt to Hartley, bodily action is touched on only in the last chapter of the book, on “The Will.” But to an attentive “observer of man,” it should be obvious that we live by doing, by performing tasks that depend on repertoires of perfected movement, some (like walking) mastered in infancy, others (like typing) later in life.