 In the 1936–37 article, “Testability and Meaning” Carnap called the partial definitions themselves “reduction sentences” and the system of definitions of theoretical terms, both partial and complete, as a reduction of the theoretical terms to the observational basis. Plainly he means by the word ‘reduction’ something other than what we currently mean, not that there is anything univocal about current uses of the word. By ‘reduction’ of vocabulary A to vocabulary B Carnap means the specification of the inferential relations that would allow us to say what sentences or combinations of sentences in A would count as evidence for sentences in B.