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January 30, 2000

Remembering Karl Popper

A reflection on the life of former Hoover fellow Karl Popper, one of the past century’s greatest thinkers. By Piers Norris Turner.

photo: Karl Popper Karl Popper  

One person’s life can sometimes tell the story of an entire century. Such is the case with Sir Karl Popper (1902–1994), one of the foremost critics of authoritarianism in the twentieth century, yet also arguably the premier philosopher of science during a century of unparalleled scientific discovery.


In 1989, the fall of the Berlin Wall brought renewed interest in Popper’s major contribution to political philosophy, The Open Society and Its Enemies. When The Open Society appeared in England in 1945, Popper was an obscure Austrian philosopher of science living in New Zealand. The book had been rejected by some twenty publishers before Friedrich von Hayek encouraged Routledge to publish it. Popper called the book his "war effort," an attempt to criticize the ideas underlying the twin ideological horrors of fascism and communism. He was concerned that well-meaning people could be induced into believing what he saw as dangerously erroneous doctrines. Although compelled to leave his native Austria in the 1930s (because of his Jewish ancestry), his book is remarkably free from personal bitterness or sadness. It is not a memoir but a philosophical broadside against utopian thinking. Popper challenged the dangerous ideas that, at the time he wrote, seemed poised to engulf the world. He did not shrink from tracing the sources of those dangerous ideas to Marx, to Hegel, and even to that greatest of all philosophers, Plato. At a time when many intellectuals had lost faith in democracy, Popper offered a spirited defense of democratic principles and outlined a compelling vision of a society grounded in democratic reforms.

Popper was a fallibilist, one who perceives great error and danger in any theory of knowledge—or regime—that claimed to offer certain truth. In such a system, there would be no incentive to establish social and political structures that promote learning or the free exchange of ideas; truth is already at hand. In the name of historical progress, the regime may then justify the squelching of human freedoms and even atrocities on a grand scale. Consequently, Popper fought against those who claimed to know the historical laws of change, a false doctrine Popper called historicism. Historicist prophecies were a threat to the open society, and, indeed, both nazism and Soviet-style totalitarianism alike produced unimaginable horrors.

Despite its success in articulating the inherent threat of Marxism, Popper’s book is not about Soviet Russia or conceived of as a Cold War tome. In fact, Popper developed his ideas just before World War II, in a radically different geopolitical landscape. Yet, soon after it appeared, The Open Society was denounced by philosophy professors for its irreverent exposition of the authoritarian tendencies in Plato and Marx. Other intellectuals were dismissive, not surprisingly since many were for too long blind to the failures of Soviet communism and indignant at any comparison of Marxism with fascism. Nevertheless, Popper’s Open Society has always had a wide readership and influential champions on both the left and the right. Isaiah Berlin wrote in 1963 that Popper’s Open Society contained "the most scrupulous and formidable criticism of the philosophical and historical doctrines of Marxism by any living writer." National Review recently ranked the book number six on its list of the hundred most important nonfiction works of the century. George Soros, who first encountered The Open Society as Popper’s student at the London School of Economics, founded the Open Society Institute to propagate Popper’s ideas, particularly in Eastern Europe. Thus the political philosophy Popper first articulated before the start of the Cold War is now being studied and put into practice in countries newly emerging from behind the Iron Curtain.


Born in 1902, Popper came of age in Vienna in the turbulent aftermath of World War I. He left school at age sixteen and began auditing lectures at the University of Vienna. Although a Marxist as a teenager, he was repelled in 1919 by the leftist-inspired street violence of postwar Vienna that resulted in the deaths of demonstrators. That same year, he studied Freud’s psychoanalysis and worked for a time with psychiatrist Alfred Adler. Popper became interested in the psychology of learning and decided he wanted to become a schoolteacher. In 1919, Popper began closely following Arthur Eddington’s successful test of Albert Einstein’s general theory of relativity. He noted how Einstein’s critical attitude toward his own theory (despite its success) was in stark contrast to the "dogmatic attitude" he found among Marx, Freud, Adler, and their followers.

In 1922 he matriculated at the University of Vienna. To support himself, he apprenticed himself to a cabinetmaker and took up social work. Pursuing his goal of becoming a schoolteacher, Popper subsequently returned to the university. In 1928, he earned a Ph.D. in philosophy and, in 1929, a teacher’s certificate. Beginning in the late 1920s, Popper began interacting with members of the famous Vienna Circle of logical positivists, a group of prominent intellectuals trying to articulate the importance of science for philosophy. Shortly after publishing (in German) a then little-noticed but classic work on the logical foundations of science in 1934, Popper left Austria under the threat of Nazi anti-Semitism. From New Zealand, where he had obtained a university teaching post, he returned to England after World War II as professor of philosophy of science at the London School of Economics, where he remained until his retirement.


Popper was concerned with the limits of knowledge and the sorts of structures needed to promote the growth of knowledge despite those limits. In both science and politics, Popper was critical of the positivism that dominated many fields of inquiry early in the twentieth century, for it assumed that knowledge was limited to that which could be empirically verified, by induction. Positivism claimed that meaningful statements are those that are verifiable. But Popper noted that verification of a universal theory would require a positive result in every possible instance, most of which would forever remain in the unobserved future, and as such can never be known for certain. For Popper, infallible foundations of knowledge—for instance, sense experience and intuition—are unavailable. On this point, Popper made the salient observation that our perceptual and mental capacities are restricted by evolution to a particular, limited understanding of the world around us. We are not gods. Popper and others also noted that the positivists’ verification principle itself could not be verified and therefore did not count as meaningful according to its own standard!

Yet in accordance with this dominant positivistic view of science, both Marxism ("scientific" socialism) and Freudianism were purported to be scientific theories by their proponents, who seemed able to interpret every possible circumstance as confirmation of their theories and thus insulate themselves from criticism. Although these verifications carried little weight, they tended to produce convictions of certainty. In contrast, Popper argued that what made theories scientific was their falsifiability, or their possibility of being refuted. Only when a theory could be wrong is it impressive that it survives testing and criticism. Popper therefore sought to delineate the philosophical underpinnings that distinguish natural sciences such as Einstein’s physics from the pseudosciences—Marxian "scientific" socialism, psychoanalysis—he had come to reject. His political and scientific philosophies are thus deeply connected through his early experiences with Marxism and psychoanalysis.

Popper argued that progress requires a critical structure within which competing theories can be tested. Popper captured his philosophy, called falsificationism or critical rationalism, with the motto "I may be wrong and you may be right, and by an effort, we may get nearer to the truth." Instead of attempting futilely to verify or justify our theories, Popper claimed we should try to falsify them since we need only a single negative instance to refute a universal theory. Consequently, what matters in rational debate is that different positions are open to criticism, which becomes the engine of progress by removing from consideration false theories, leaving only the provisionally best theories behind. The "best" theories could still not be verified or justified, but since they had not been falsified either, they would be preferable to falsified theories. The rationality of holding a particular position would be granted to the extent to which the theory is open to criticism. This makes possible not only progress but also optimism, which is for Popper a moral duty.

Popper’s central insight, inspired by Socrates, is that we can never know anything for certain, which has important consequences for the way we approach the theory of knowledge and critical debate in general. Popper argued that this ought to humble us and cause us to understand our limitations. He wrote, "We know nothing—that is the first point. Therefore we should be very modest—that is the second. That we should not claim to know when we do not know—that is the third."


The fear is that, when we assume we have certain knowledge in our hands, we become arrogant. With this arrogance comes the danger that we will feel justified in repressing those who disagree. When an entire government is infused with this arrogance, the threat is magnified. Since this certainty is unachievable, and the arrogance unjustified, Popper tried to show what sort of political structure would best allow for social improvement once we accept the limits of knowledge.

Popper applied critical rationalism in politics by advocating piecemeal social engineering in an open society. We cannot be sure we have attained truth, but with effort, we should be able to improve our society by rectifying identifiable problems. For Popper, philosophy and politics begin with an effort to solve problems. Improved solutions and policies are achieved through a process of creative conjecture and intersubjective criticism, a process that requires us to develop arguments and articulate policies as boldly and clearly as possible. For this process to work well, we need to maintain free and critical institutions and individual liberties. We also need a system of government amenable to peaceful change (i.e., democracy), which would be favored, in part, because it allows for a plurality of views to be considered in the marketplace of ideas.

photo: Karl Popper The papers of Friedrich von Hayek and Karl Popper, both former Hoover fellows, are housed in the Hoover Institution Archives. Two of the twentieth century’s best-known thinkers, they were friends for half a century. The personal and intellectual exchanges in these postcards and letters document their remarkable relationship. Both were native Austrians who spent their academic careers in the English-speaking world. Hayek helped Popper publish his early work in England and found him a position at the London School of Economics, where Hayek was also a professor. Comrades in arms against authoritarianism, their works were similar in many respects, Hayek even writing to Popper of "our" philosophy.

Despite Popper’s strong criticisms of Marxism’s historicism and tendency toward totalitarianism, he was sympathetic to Marx’s moral impulse. He wrote,

if there could be such a thing as socialism combined with individual liberty, I would be a socialist still. For nothing could be better than living a modest, simple and free life in an egalitarian society. It took some time before I recognized this as no more than a beautiful dream; that freedom is more important than equality; that the attempt to realize equality endangers freedom; and that, if freedom is lost, there will not even be equality among the unfree.


Popper is likely to be remembered as one of the greatest philosophers of the twentieth century for his contributions to both political and scientific thought. Many of his insights have become part of common sense, which is perhaps one reason he is not better known. We often hear of efforts to "falsify" some theory or another without any reference to the man who introduced the notion that science is marked by the method of falsification, and the phrase open society is part of everyday parlance. Today, partly because of Popper, nearly all philosophers are fallibilists in some sense or other, recognizing the failure of positivism. (Some philosophy students are unimpressed with Popper because many of his ideas seem so obvious.)

The reluctance of the philosophical profession to adopt Popper’s ideas stems at least in part from the fact that, beneath the surface appearance of common sense, much of his philosophy is counterintuitive. Most philosophers believe positive foundations can be provided for reasonable debate and therefore see no need for Popper’s conjectural, criticism-driven method. They argue that justification, as far as could reasonably be required, is possible. Other philosophers believe that no rational debate is possible at all and so think Popper too optimistic. His philosophy of science also has been attacked as failing to represent how science is done. Critics argue that induction is a key to scientific progress and rational decision making about future action. His political theory does not provide a single, systematic worldview, and Popper has been interpreted differently by writers from divergent political perspectives, partly because he is sketchy about some details. Although this may be seen as one of his work’s merits, and entirely consistent with his antidogmatic tone, it also partly accounts for his failure to attract more disciples and discussion.

Popper skillfully criticized a great number of mainstream philosophical positions. He made few friends and fewer converts within the profession. He even had fallings-out with many of his own best students. One of his colleagues remarked jokingly that Popper’s book should have been called The Open Society by One of Its Enemies. Few of Popper’s followers became influential professors at major universities, which has left Popperian studies in the hands of a small number of serious philosophers. Despite these criticisms and setbacks, Popper continues to be popular among general readers the world over. His calls for open-mindedness and the free exchange of ideas will continue to capture the attention of future readers. Popper also left a legacy of papers and unpublished work, housed at the Hoover Institution, where he had been a fellow. His works, filled with important insights, mean that Popper will be one of the few twentieth-century philosophers to be read well beyond his lifetime.

Piers Norris Turner is a research assistant at the Hoover Institution.

Special to the Hoover Digest. The author would like to thank Thomas H. Henriksen, Abigail Norris, Jeremy Shearmur, and David Turner for their beneficial comments.