But it is the same specimen; and the same chemical elements and the same quantities of those elements are present within the case at the end as were present at the beginning.

Again the engineer and the astronomer deal with the motions of real permanences in nature.

Any theory of nature which for one moment loses sight of these great basic facts of experience is simply silly.

But it is permissible to point out that the scientific expression of these facts has become entangled in a maze of doubtful metaphysics; and that, when we remove the metaphysics and start afresh on an unprejudiced survey of nature, a new light is thrown on many fundamental concepts which dominate science and guide the progress of research..