Abstract: In his Logische Aufbau, Rudolf Carnap presented a structuralist philosophy of science. Carnap exhibited a fluctuating awareness of the difficulty besetting that programme, and of the limited options his epistemology allowed for escape. The option he finally chose has the form of solution that Newman suggested, somewhat ironically, to Russell. But Carnap attempted simultaneously to refer to experience and to claim that the notions he needed are experience-independent. The basic problem returned after some decades when Hilary Putnam put it to good use in his seminal critique of metaphysical realism. It is argued that in both cases, a dissolution of problem is possible with the introduction of indexical reference.

Keywords: Rudolf Carnap, Logische Aufbau, Putnam, Hilary Putman, structuralism, indexical reference, David Lewis,