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. Talcott Parsons
The main concern of the study is with the outline of a theoretical system. Its minor variations from writer to writer are not a matter of concern to this analysis. Talcott Parsons
The system becomes logically closed when each of the logical implications which can be derived from any one proposition within the system finds its statement in another proposition in the same system. Talcott Parsons
Thus, in general, in the first instance, the direction of interest in empirical fact will be canalised by the logical structure of the theoretical system. Talcott Parsons
