A stranger in his homeland even before emigrating in 1937, the philosopher Karl Popper is rarely considered an Austrian. Although he was born in Vienna in 1902 and buried there in 1994, he is known as an Atlantic intellectual and an anti-Communist prophet of postwar liberalism. He first became famous for The Open Society and Its Enemies (1945). 1 He wrote the book during World War II in his New Zealand exile, intending it as a defense of democracy against fascism. The defeat of Austrian socialism and the collapse of Central European democracies were the major experiences informing his analysis. But The Open Society quickly became, with Popper’s full support, a charter of Atlantic Cold War liberalism. His philosophy of science, exemplified best in Logik der Forschung, went through a similar transformation. 2 To be sure, it is commonly debated in the context of logical positivism and the Vienna Circle; but the circle’s emigration and the postwar triumph of analytic philosophy in the Anglo-American academy transformed positivism, too, into an Atlantic philosophy. The “fugue of exile’s disruptions” severed the thread connecting Popper to Austria. 3

Yet Popper was the foremost philosopher to carry the progressive Viennese legacy into the postwar era. In his critiques of the Vienna Circle and Red Vienna he confronted the philosophical and political problems of Viennese late enlightenment [End Page 711] and the interwar crises of scientific reason and Central European democracy. Refashioning the fin-de-siècle progressive legacy, he drew novel visions of liberal science and politics, imagining utopian scientific and political communities that were engaged in the pursuit of truth and reform. He made critical debate the acid test of political and scientific rationality, the center of a new liberalism. Establishing a free public sphere as the sine qua non of the Open Society, he innovated on a familiar liberal motif, shared by thinkers as different as Kant, De Staël, Guizot, Mill, and Habermas.

In The Open Society Popper also wrote the political platform of the postwar Social-Democratic Consensus that legislated for the welfare state and mobilized against Communism. During World War II he opted for a liberal-socialist alliance that would contain postwar Central European fascism. Instead, his “Popular Front” platform proved adaptable to postwar anti-Communism. He made a few naïve pronouncements on deterrence and the free world during the Cold War. 4 They reflect badly on his political philosophy. Yet disentangled from its Cold War associations, his liberalism contains an abiding cosmopolitan vision for an age that is looking beyond the nation-state. His cosmopolitanism originated as a solution to dilemmas of ethnic identity faced by the assimilated-Jewish Viennese intelligentsia. His Open Society expressed their dream of integration into a community that discounted religion, ethnicity, and nationality. 5 He refused to give up on cosmopolitanism in the bipolar world when Machtpolitik seemed the order of the day. Almost alone among postwar liberals, he retained a belief in an international legal order and challenged national self-determination. His vision has regained relevance today. Cosmopolitanism and critical debate provide a starting-point for renegotiating liberal dilemmas.

“My theory of knowledge, my philosophy of science and my political philosophy are original only in their interdependence,” stated Popper in a 1976 interview. 6 His epistemology has major political and scientific significance. Well before cultural studies began deconstructing science, Popper countered philosophers’ and scientists’ claims of expertise. There is no philosophical method. Every person is a problem-solver, and so every person is a philosopher. “Science is nothing but enlightened and responsible common sense—common sense broadened by imaginative critical thinking.” 7 Demystifying science, he never gave up on the growth of knowledge. He conceived of science as an unending quest for uncertain but growing knowledge. A non-foundationist, [End Page 712] he insisted that objectivity meant intersubjectivity. Rationality was a product of critical debate. In today’s intellectual world, devoid of certainty, where systems of knowledge and identities have been thrown into flux, Popper’s unique synthesis of contingency, convention, and change with logical certainty, objectivity, and tradition suggests a promising direction in the...