 Neurath’s protocols didn’t have the atomic structure and the atomic testing role of Carnap’s. Their methodological role reflected Duhem’s holism: hypotheses are not tested individually; only clusters of statements confront empirical data. But their methodological value in the testing of other statements didn’t make them unrevisable. This is Neurath’s anti-foundationalism: Insofar as they were genuinely scientific statements, consistency with the spirit that opposed science to dogmatic speculation and, no less importantly, opposed naturalistic attention to actual practice, required that protocols too be testable. This is the so-called Neurath Principle: in the face of conflict between a protocol and theoretical statements, the cancellation of a protocol statement is a methodological possibility as well (Neurath 1932/1983, 95, Haller 1982). The role of indeterminacy in the protocol language points to a distinction between a special Neurath Principle and a general Neurath Principle (Cartwright et al. 1996, 202–6). In the former, and earlier, Neurath assumed a determinate logical relation of inconsistency. In the latter, subsequent version, the scope of relations between hypotheses and protocol statements extended to indeterminate relations such that the principle behind the epistemic status of protocol statements is simply grounded on the voluntarisitic and conventionalist doctrine that ‘[a]ll content statements of science, and also their protocol statements that are used for verification, are selected on the basis of decisions and can be altered in principle’ (Neurath 1934/1983, 102). Carnap adopted a similar conventionalist and pragmatic attitude in ‘On Protocol Sentences’ (1932/1987) and in Logical Syntax (1934). The complex structure of the explicitly laid out protocol would serve, in the holistic Duhemian spirit, the purpose of testing it by making explicit as many circumstances as possible which are relevant to the experience, especially as sources of its fallibility (was Otto hallucinating? were all the parts of the experimental instrument working reliably? etc.). Neurath’s dictum was meant to do justice to actual scientific practice with regard to the role of experimental data.