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. – Talcott Parsons

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. – Talcott Parsons

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