 David Hartley (1705–57) is the author of Observations on Man, his Frame, his Duty, and his Expectations (1749)—a wide-ranging synthesis of neurology, moral psychology, and spirituality (i.e., our “frame,” “duty,” and “expectations”). The Observations gained dedicated advocates in Britain, America, and Continental Europe, who appreciated it both for its science and its spirituality. As science, the work grounds consciousness in neuro-physiology, mind in brain. On this basis, the central concept of “association,” much discussed by other British philosophers and psychologists, receives distinctive treatment: the term first names the physiological process that generates “ideas,” and then the psychological processes by which perceptions, thoughts, and emotions either link and fuse or break apart. In keeping with this physiological approach, Hartley offers a conceptually novel account of how we learn and perform skilled actions, a dimension of human nature often left unexplored in works of philosophy. Such actions include those involved in speech—and, by extension, the conduct of scientific inquiry. As a work on the spiritual condition of humanity, Hartley’s Observations affirms universal salvation—the assurance that all people will eventually become “partakers of the divine nature.” In this regard, it presents an original model of psychological growth, which describes how the self both forms and transforms, as the person gains in “sympathy” and “theopathy”—put simply, learns to love, both others and God.