or the reform of logic; it was Carnap and Wittgenstein who brought these into
the center of attention at Vienna. The central members of the Vienna Circle
were network hybrids of physicists and mathematicians who also had had
Neo-Kantian teachers.
Physicists were emboldened that they had something attention-getting to
say in the central territory of philosophy. Soon they launched into an attack
on the dominant school, neo-Kantianism itself. In the process they found it
convenient to wave the banner of Mach. When the Vienna Circle formalized
in 1928, it called itself the Ernst Mach Society. This was to a certain extent
rhetorical. The methods of the Vienna Circle, especially their logical tools, were
not those of Mach and his psychological reductionism; and the physicalism of
the 1930s was far from Mach’s neutral monism. Phenomenalism was one
theme among many explored by the circle. It was above all Mach’s militancy
that they invoked, now widened to exclude metaphysics not only from physics
but from everywhere.
The first vehicle of this militancy was verification, a concept already
launched by Schlick in pre-Circle days, in 1918, before he became a positivist.
As Carnap, Wittgenstein, and others joined in, more resources were brought
to bear on how scientific knowledge is constituted and how it differs from the
forms of non-knowledge that are to be excluded. This proved to be a fruitful
vein of puzzles, as each solution gave rise to new difficulties. Empirical verifica-
tion foundered on questions about the nature of ultimate verifiers and the
status of the principle of verifiability itself. Russellian logicism provided a
criterion for rejecting some forms of expression as not merely false but mean-
ingless; Schlick and Waismann shifted to meaningfulness as the demarcation
between science and non-science. This in turn raised the question of the
meaningfulness of the language in which the criterion itself was formulated.
Popper eventually carried this internal conflict into a rejection of the verifica-
tion program while continuing the demarcationist spirit that was the core of
the Vienna Circle.Rival Networks of Mathematical
Foundations and the Genesis of Gödel’s Proof
The 1920s were also the height of conflict over mathematical foundations, the
most active period for pronouncements by Brouwer, Hilbert, and their sup-
porters. Alongside them remained a third (and indeed the oldest) faction, the
Russell-Frege logicists, whose stronghold in the 1920s had become the Vienna
Circle. Their conflicts became superimposed on those of the physicist-philoso-
phers who first constituted the Circle, building to a grand intensity of creative
struggle in the years around 1930.724 •^ Intellectual Communities: Western Paths