Of the four philosophers considered in the preceding chapter, three were professional teachers of philosophy, and the fourth only just missed being appointed to a professorship. Of the seventeen philosophers dealt with in the present chapter, only two were University teachers, and the rest were amateurs; but not in the derogatory sense of the term, for much of the best work of the period, in science as well as in philosophy, was done by amateurs. It was characteristic of the Age of Enlightenment that almost every person of education tried to be philosophical; and philosophy came to be regarded as essentially a matter of common sense in search of secular world-wisdom, and relying on itself instead of on authority. Moreover, people were not particularly interested in abstract philosophy as such; they used it mainly as an instrument of religious and political reform. All literature tended to become philosophical more or less, even when it did not take the form of Pope’s didactic poem, Essay on Man (1733), which was planned as part of a complete exposition of the kind of deistic philosophy taught by Lord Bolingbroke (1672–1751), and which at all events admirably expressed the philosophic temper of the age in the familiar verse, “The proper study of mankind is man.” In a general history of the culture of the eighteenth century many more writers would have to be considered, particularly Jean Jacques Rousseau (1712–78), whose sentimental outpourings helped to precipitate the French Revolution (1789). Something would also have to be said about the influence of the Salons. In the present work, however, we are only concerned with what is required for an understanding of the philosophic background of the science of the eighteenth century, and we are not concerned with the religious and political or social controversies of the period. No doubt the secular tendency helped to spread an interest in science, and to help its advancement in various ways. But for the special purpose of this volume a selection of leading representatives of the period will be sufficient; and the selection actually made may be regarded as a very fair sample, not because the selection has been made at random, but because it has been made with care. The grouping of these representative philosophers is a matter of some difficulty, as most of them had a common practical aim, and many of them weresomewhat nebulous about distinctions which are of peculiar interest to expert philosophers; but some kind of orderly grouping is always helpful, and the grouping actually adopted is reasonably fair.