Labor was an analytic category in the long english eighteenth century, but was work equally so? Is there any point in discovering a difference between the two? Lawyers and high-court judges, philosophers, physiologists, and prelates worked hard at the business of defining labor, over many years. Their formulations provided the legal and conceptual underpinnings of a new form of society born of the era of revolutions (political, philosophical, industrial; American, Atlantic, French). Here was a template for social knowledge in an emerging class society. Society was divided into propertied and propertyless; the propertyless were compelled by material need to put their labor at the disposal of the propertied. The labor of the poor was a country's natural resource, like its soil and seas and mines; it fell to the propertied to deploy this resource for the national benefit. British philosophers and physicists analyzed labor as a form of energy, often drawing an analogy between it and another great resource of the nation, its horses. Working men and women and horses were bound together in the deep structure of political thinking about labor and the social order. For eighteenth-century theorists, legislators, and farmers, the horse was the immanent measure of labor power and labor time. A horse was a measure of labor itself. There were perhaps a million horses in England and Wales in the late eighteenth century, about half of them workhorses in farming. The contribution of their dung to cereal-crop yield is attested to by economic and agricultural historians (Wrigley, Continuity 35–46; Gerhold; Turner). Horses were one reason the nation was, by and large, able to feed an increased population out of its own natural resources and sources of labor power, unlike other European countries in the period 1660–1820 (Wrigley, Poverty 44–67). The importance of the horse to agricultural productivity seems assured, though some contemporary economists, in the face of harvest failures in the 1790s and ongoing crises of dearth, complained of too many horses and of the vast amount of grain and labor spent in foddering and caring for them (Crafts; Brooke 1–34).