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

It is probably safe to say that all the changes of factual knowledge which have led to the relativity theory, resulting in a very great theoretical development, are completely trivial from any point of view except their relevance to the structure of a theoretical system.

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

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.

But the fact a person denies that he is theorising is no reason for taking him at his word and failing to investigate what implicit theory is involved in his statements.

The implications of these considerations justify the statement that all empirically verifiable knowledge even the commonsense knowledge of everyday life - involves implicitly, if not explicitly, systematic theory in this sense.

Special emphasis should be laid on this intimate interrelation of general statements about empirical fact with the logical elements and structure of theoretical systems.