 The project of providing analyses in this way of especially problematic concepts like those concerning, for example, material objects, knowledge, perception, causation, expectation, freedom, and the self, was pursued by Positivists and other analytic philosophers for a considerable period (see Carnap 1928 [1967] for some rigorous examples, Ayer 1934 [1952] for more accessible ones). With regard to material object claims, the program came to be known as “phenomenalism”; with regard to the theoretical claims of science, as “operationalism” ; and with regard to the claims about people’s mental lives, “analytical behaviorism” (the relevant experiential basis of mental claims being taken to be observations of others’ behavior). Although these programs became extremely influential, and some form of the verifiability criterion was often (and sometimes still is) invoked in physics and psychology to constrain theoretical speculation, they seldom, if ever, met with any serious success. No sooner was an analysis, say, of “material object” or “freedom” or “expectation,” proposed than serious counterexamples were raised and the analysis revised, only to be faced with still further counterexamples (see Roderick Chisholm 1957, and Fodor 1981, for discussion). Despite what seemed its initial plausibility, philosophers came to suspect that the criterion, and with it the very notion of analyticity itself, rested on some fundamental mistakes.