The fact that modern science has long ceased to be a ‘natural’ science is something which has begun to dawn upon the modern scientific researcher himself. What has thus come to him as a question finds a definite answer in the picture of electricity we have been able to develop. It is again Eddington who has drawn attention particularly to this question: see the chapter, ‘Discovery or Manufacture?’ in his Philosophy of Physical Science. It will be appropriate at this point to recall his remarks, for they bear not only on the outcome of our own present discussion, but also, as the next chapter will show, on the further course of our studies.