WHAT IS ENLIGHTENMENT?
The Johnstones lived at the edges of empire and at the edges of the enlightenment. The brothers and sisters were not themselves philosophers or chemists or historians; only Elizabeth Carolina wrote a work of literature that was published, and only William wrote a political pamphlet of any substantial pretention (about his thoughts on the American conflict, in 1778, and on the unlikelihood that the colonists, with their “uncertain theory” of a new system of government, would be able to establish “a new and independent empire”).1 But the Johnstones were friends or acquaintances of the philosophes of eighteenth-century Edinburgh, including David Hume, Adam Smith, and Adam Ferguson. They lived in the “atmosphere of society,” in Adam Ferguson's expression, in which “minds should become enlightened, in proportion as they should have occasion to receive information from the frequent discussion of subjects, which they are concerned to understand.”2
In the Scotland to which the Johnstones returned, there were at least three different senses of enlightenment, or of “lights.” There was the sect of philosophers of the science of nature and human nature.3 There was the milieu of the enlightenment, in the sense of the assortment of booksellers, printers, proof-correctors, itinerant tutors, lawyers, advocates’ clerks, translators, and editors who constituted the business of enlightenment in Scotland as in France: the individuals by whom the lights of science were communicated.4 There was the