He applied “Page 99 Test” to his new book, The Moral Culture of the Scottish Enlightenment, 1690–1805, and reported the following:
On page 99 of The Moral Culture of the Scottish Enlightenment, 1690 - 1805 I discuss the importance of so-called 'natural religion' for Enlightenment moral philosophy. This is one of the central themes of the book. As I show, the role of natural religion within Scottish Enlightenment culture was very different from what it is often thought to be.Learn more about The Moral Culture of the Scottish Enlightenment, 1690–1805 at the Yale University Press website.
In the eighteenth century, the term 'natural' (or 'reasonable') religion was used to refer to those religious beliefs that could be known from human reason and experience, without the assistance of the Bible. Such beliefs included the existence of a single, omnipotent deity; divine providence; and an afterlife with rewards and punishments that reinforce good conduct in this life.
This natural religion is often associated with moderate enlightened thinkers in the eighteenth century, who were not atheists, but did not adhere to conservative, orthodox religious beliefs either. In the Scottish Enlightenment, as elsewhere in Europe, many of these enlightened thinkers were clergymen. In addition to pursuing careers within the Calvinist Church of Scotland, they made some of the most influential contributions to the secular world of letters in the eighteenth century, publishing on subjects such as history (William Robertson), morality (Adam Ferguson, Thomas Reid), and literary criticism (Hugh Blair).
It seems plausible to argue that these enlightened and intellectually sophisticated clergymen must have been sympathetic to natural religion, because it represented a more rational, philosophical form of religious belief, and that their orthodox, conservative opponents would have been opposed to it, because they were concerned to defend the authority of Biblical revelation.
But in fact, as I show in the book, the positions of 'enlightened' and 'orthodox' thinkers on natural religion within the Scottish Enlightenment were the reverse of what they are usually believed to be. Enlightened clerics such as William Robertson or Hugh Blair were very skeptical about the possibility of a natural religion, while the strongest proponents of natural religion were to be found among the conservative, orthodox critics of these enlightened clergymen. The skepticism of enlightened clerics about natural religion was less extreme than that of their famous contemporary, the philosopher David Hume. Yet, it was not wholly dissimilar to his.