 Carnap…distinguished two languages: a ‘monologizing’ one (phenomenalist) and an ‘intersubjective’ (physicalist) one. (…) only one language comes into question from the start, and that is the physicalist. One can learn the physicalist language from earliest childhood. If someone makes predictions and wants to check them himself, he must count on changes in the system of his senses, he must use clocks and rulers, in short, the person supposedly in isolation already makes use of the ‘intersensual’ and ‘intersubjective’ language. The forecaster of yesterday and the controller of today are, so to speak, two persons. (Neurath 1931/1983, 54–55)