The use of a term such as 'nineteenth-century rationalism' inevitably suggests that one is dealing with a coherent philosophical system or movement, of which the principles as well as the followers may conveniently be listed. However, a proper understanding of Robertson's work can only be achieved by viewing him in the light of the rationalist tradition, so an attempt to distil something like the 'rationalist spirit' from Victorian intellectual history is still required. At first glance, the French philosopher Auguste Comte seems a decidedly unlikely candidate for the position of father of nineteenth—century British rationalism, even apart from his nationality. Nearly all those 'professional' scientific naturalists felt that they were backed by a scientific theory of vast promise and implications: Darwin's theory of evolution, as expounded in his Origin of Species of 1859. Charles Darwin's own grandfather, Erasmus Darwin, had put forward evolutionary ideas in his Zoonomia, a work in verse.