 Wittgenstein greatly influenced the Vienna Circle. The ‘official’ positivist theory of mathematics, as it were, is not a formalist one. Mathematical theorems express truths, albeit in a special way: true by virtue of meaning alone. The most influential positivist has been Carnap, if one does not classify Quine as a positivist (but Quine’s views, in the 1930s at any rate, were very close to Carnap’s, indeed arguably Quine remained truer to Carnap’s radical empiricism than Carnap did). And one can certainly discern strong elements of formalism in some of Carnap’s writings, for instance in Logische Syntax der Sprache (1934 [1937]) and ‘Empiricism, Semantics, and Ontology’ (1950 [1956]).