Carnap’s and Quine’s debate on semantic austerity: Revaluing their empiricist extensionalism

In this paper I will show why Carnap’s and Quine’s sympathy for the extensionality thesis can be considered equivalent to their concern with clear logical criteria for the manipulation—that is, identification and permutation—of empirical linguistic terms and also why Carnap renounced to the extensionality thesis in the late 1930s. Quine’s inclination to see extensionality as an avoidance of semantic confusion triggered his profound admiration for Carnap’s early works, which are very much of an extensionalist nature. But Quine realizes, as early as the 1930s, that Carnap does not have the same resistance to admitting intensional objects. Already in the Aufbau (1928), Carnap’s phenomenalist and structuralist approach to knowledge, and his pragmatic approach to language systems, leads to the conclusion that the self-psyche and others’ psyche are not something, in principle, inaccessible to knowledge, and, therefore, that intensional—including intentional—objects could, in principle, be scientific objects. In addition to the historical development of semantics—which influenced Carnap—there are two fundamental reasons for Carnap’s increasing tolerance of intensional terminology and analysis in the philosophy of language. In the first place, Carnap thinks it possible to maintain a discourse on intensions without this leading to an ontological commitment to abstract intensional entities. Second, the behaviourist criteria for the identification of intensions that he offered demonstrates that he believed it possible to meet clear identification criteria for intensions. I will show why Carnap disagrees on these two points, in his semantic period, with Quine.