 Carnap’s attempt to address this problem by ramseyfication was published in several places from 1958 onwards. (See Carnap 1958, 1963, §24C-D and the popular exposition 1966, Chs. 26 and 28; compare Ramsey 1929 and see Psillos 1999, Ch.3. This proposal and a variant of it (1961b) were both presented in his 1959 Santa Barbara lecture (published in Psillos 2000a); as it happened, Kaplan presented his criticism (1975a) of Carnap’s 1956 criterion at the same conference.) With ramseyfication Carnap adverted again to entire theories as the unit of assessment. Ramseyfication consists in the replacement of the theoretical terms of a finitely axiomatized theory by bound higher-order variables. This involves combining all the theoretical postulates which define theoretical terms (call this conjunction T) and correspondence rules of a theory which link some of these theoretical terms with observational ones (call this C) in one long sentence (call this TC) and then replacing all the theoretical predicates that occur in it by bound higher-order variables (call this RTC). This is the so-called Ramsey-sentence of the entire theory; in it no theoretical terms appear, but it possesses the same explanatory and predictive power as the original theory: it has the same observational consequences. However, Carnap stressed that the Ramsey sentence cannot be said to be expressed in a “simple” but only an “extended” observational language, for due to its higher-order quantificational apparatus it includes “an advanced complicated logic embracing virtually the whole of mathematics” (1966, [1996, 253]).