 This concern with empirical content also explains why Bridgman was not content with the mainstream post-positivist philosophical discourse on concept-formation and empirical significance, exemplified by the works of Carl Hempel and Willard Van Orman Quine. As noted in Section 2.2, Bridgman did not object to theoretical science creating a system of concepts and laws that made contact with observations only at some points. However, Quinean holism, in which the unit of empirical significance was the entire system of knowledge, had no particular concern about increasing the number of those points-of-contact with experience. Bridgman’s ideal was to operationalize each and every concept if possible, and each case of de-operationalization rang alarm bells in his head.