This first major Engish treatise on Physiocratic economic theory sets forth the principal doctrines of what Gray calls "the system of the Economists." He takes issue not only with Adam Smith's attribution of economic surplus to manufacture and trade as well as agriculture, but more especially with the contrary views on taxation of Arthur Young. Gray bolsters the position of proprietors in the physiocratic weltanschauung by designating them an essential class along with cultivators.