 One of Blair’s colleagues at Edinburgh University was Adam Ferguson (1723–1816). He succeeded David Hume as librarian of the Advocates’ Library in Edinburgh and then held in succession two chairs at Edinburgh University, that of natural philosophy (1759–1764) and of pneumatics and moral philosophy (1764–1785). His lectures at Edinburgh were published as The Institutes of Moral Philosophy (1769) and Principles of Moral and Political Science (1792). Ferguson advocates a form of moral science based on the study of human beings as they are and then grounds a normative account of what they ought to be upon this empirical basis. His most influential work is An Essay on the History of Civil Society (1767). There Ferguson attended to one of the main concepts of the Enlightenment, that of human progress, and expressed doubts about whether over the centuries the proportion of human happiness to unhappiness had increased. He believed that each person accommodates himself to the conditions in his own society and the fact that we cannot imagine that we would be contented if we lived in an earlier society does not imply that people in earlier societies were not, more or less, as happy in their own society as we are in ours. As against our unscientific conjectures about how we would have felt in a society profoundly unlike the only one we have ever lived in, Ferguson commends the use of historical records. He talks disparagingly about boundless regions of ignorance in our conjectures about other societies, and among those he has in mind who speak ignorantly about earlier conditions of humanity are Hobbes, Rousseau, and Hume in their discussions of the state of nature and the origins of society.