Whitehead's philosophy of nature is largely presented in his books An Enquiry concerning Natural Knowledge (PNK) and The Concept of Nature (CN), and to some extent in The Principle of Relativity (P of R), although the latter is also concerned with his theory of relativity. One of the reasons for the neglect of these works in recent years is that philosophers of science have tended to be interested in other types of problems than those discussed by Whitehead there. They have been primarily taken up with questions relating to the linguistic analysis of science and with models of scientific theories. It is a little ironical to reflect that this approach is probably due to the influence of mathematical logic, of which Whitehead was one of the pioneers. In his philosophy of nature Whitehead, however, was concerned with a very different sort of problem, which he would have considered more fundamental, namely, the relating of the abstract notions of physics to our sense-experience.