Logical positivism
During the late 1920s to 1940s, a group of philosophers of the Vienna Circle and the Berlin Circle developed Russell and Wittgenstein's formalism into a doctrine known as "logical positivism" (or logical empiricism). Logical positivism used formal logical methods to develop an empiricist account of knowledge. Philosophers such as Rudolf Carnap and Hans Reichenbach, along with other members of the Vienna Circle, claimed that the truths of logic and mathematics were tautologies, and those of science were verifiable empirical claims. These two constituted the entire universe of meaningful judgments; anything else was nonsense. The claims of ethics, aesthetics, and theology were consequently reduced to pseudo-statements, neither empirically true nor false and therefore meaningless. In reaction to what he considered excesses of logical positivism, Karl Popper insisted on the role of falsification in the philosophy of science—although his general method was also part of the analytic tradition. With the coming to power of Adolf Hitler and Nazism in 1933, many members of the Vienna and Berlin Circles fled to Britain and the US, which helped to reinforce the dominance of logical positivism and analytic philosophy in anglophone countries.