The importance of certain problems concerning the facts will be inherent in the structure of the system.

Empirical interest will be in the facts so far as they are relevant to the solution of these problems.

If observed facts of undoubted accuracy will not fit any of the alternatives it leaves open, the system itself is in need of reconstruction.

But the scientific importance of a change in knowledge of fact consists precisely in j its having consequences for a system of theory.

A theoretical system does not merely state facts which have been observed and that logically deducible relations to other facts which have also been observed.

It is that of increasing knowledge of empirical fact, intimately combined with changing interpretations of this body of fact - hence changing general statements about it - and, not least, a changing a structure of the theoretical system.