ABSTRACT
By ‘data language’ is meant the language used to describe the evidence which is adduced in support of any theory or law. Thinkers may have certain theoretical terms which are not commonly accepted, but as long as these are clearly interpreted in terms of the expressions of the data language, others will understand what is being said and can verify it. Carnap had physics mainly in mind, of course, and he could thus speak of the theoretical language as a ‘logico-mathematical system’. Of course, it is in the nature of ‘partial interpretation’ that the people can increase the range of tests for T by extending the interpretation of the term and adding new correspondence rules. The theoretical terms of operationism are, therefore, theoretical only in a weak sense of the word. Psychologists who hold to operationism have never adequately resolved this inconsistency in their position.
