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.

If there are four equations and only three variables, and no one of the equations is derivable from the others by algebraic manipulation then there is another variable missing.

A scientifically unimportant discovery is one which, however true and however interesting for other reasons, has no consequences for a system of theory with which scientists in that field are concerned.

Spencers god was Evolution, sometimes also called Progress.

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.

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

The hypothesis may be put forward, to be tested by the s subsequent investigation, that this development has been in large part a matter of the reciprocal interaction of new factual insights and knowledge on the one hand with changes in the theoretical system on the other.