 The field that was most significantly and expressly affected by operationalism was psychology. Behaviorist psychologists took up operationalism (or operationism, as it was more often called in psychology) as a weapon in their fight against more traditional psychologists, especially those who prized introspection as the most important source of psychological knowledge. The Harvard psychologist Edwin Boring (1886–1968) saw Bridgman’s philosophy as a modern substitute for positivism, and he seems to have coined the term “operationism” (see Walter 1990, 178). It was Boring’s student Stanley Smith Stevens (1906–1973) who was perhaps the most aggressive promoter of operationism in psychology (Hardcastle 1994; Feest 2005). Stevens saw operationism as a sure method of increasing rigor in psychological experiments and discourse, asserting that “to experience is, for the purpose of science, to react discriminately”, since these reactions are what science can measure and record publicly (quoted in Feest 2005, 136). Echoing Bridgman’s take on Einstein, Stevens declared in 1935: “The revolution that will put an end to the possibility of revolutions is the one that defines a straightforward procedure for the definition and validation of concepts. … Such a procedure is the one which tests the meaning of concepts by appealing to the concrete operations by which the concept is determined. We may call it operationism” (quoted in Walter 1990, 180).