 Carnap differed from the philosophical tradition not only in his suspicion of ordinary language and its potentially misleading “philosophical” artifacts, and in his engineering impulse to replace our inherited languages by better-constructed and more precise constructed linguistic frameworks, but also in his increasingly pronounced pluralism among frameworks. In the Aufbau, Carnap had already discussed the availability of different frameworks (phenomenalist, physicalist, and more), and how they were more or less suitable for different purposes (see the supplement on  Aufbau).  But these frameworks still differed only in the choice of non-logical primitives and in the definition of non-primitive terms—the frameworks were still based on the same syntactic formation rules and on one and the same logical system. As far as the explicit endorsement of syntactic and logical pluralism and tolerance is concerned, the turning point came in 1932, while Carnap was writing his book (now often considered his masterpiece) Logical Syntax of Language. The starting point of that book, as we will see in more detail in  section 4  below, had been strongly motivated by the search for a single standard language of science. But this was now combined with Carnap’s new idea that, for philosophical statements about science, the standard of communicative acceptability should not (as in Wittgenstein’s Tractatus) be that it have meaning (that it picture some state of affairs), but that it be translatable into the “formal mode of speech”. His criterion for the scientific (non-metaphysical) status of a philosophical statement, that is, had shifted from the reducibility of a sentence to “atomic” observation sentences to its expressibility as a statement solely about linguistic artifacts (rather than about the supposed things and processes they refer to). But Carnap had still thought, until late 1932, that a single standard language for logical syntax could be found, and had invested a lot of time in devising such a language system. At that point, however, two sets of controversies attracted attention: the so-called “protocol sentence debate” about the correct form of observation sentences (and by implication, the role of observation in science), and the dispute about the foundations of mathematics among the three schools of logicism, intuitionism, and formalism. Both these controversies came to seem to Carnap, after years of involvement in each of them, to stumble over artifacts of inherited language just like the old philosophical problems the Vienna Circle thought it had swept away. He came to regard the different positions in these debates not as potentially “right” or “correct” (or “wrong” or “incorrect”) but as different proposals for language frameworks in which to frame the questions, different ways of articulating the problems surrounding empirical evidence and the nature of mathematics, respectively. And it seemed to him that these proposals were mostly not mutually exclusive; on the contrary, he came to think that many different alternative languages should be pursued and developed to see how well they perform in different contexts. He saw them as motivated by different needs and requirements, perhaps by different ultimate values, and he thought the discussion of values should not be confused with the study and development of the language frameworks themselves: “in logic”, he famously wrote in the Syntax (LSS: §17), “there are no morals”. 