The Karl Popper

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     The Myth of the Closed Mind - Video Synopsis


Founder and Editor: Dr. Ray Scott Percival

Co-Founder and Assistant Editor: Dr. Barry McMullin

Photograph: Karl Popper, Prague, May 1994

Karl Raimund Popper (1902-1994)
Photograph used by kind permission of
Dr. Milan Jira from Popper's visit to Prague, May 1994.



A video introduction to my book: The Myth of the Closed Mind. My book is a major strategic argument against the idea of the closed mind. It is a contribution to Karl Popper's critical rationalism. The closed mind thesis is the idea that some people and ideas are irrational and insulated from criticism. Religious zeal, suicide terrorism, passionate commitment to ideologies, and various psychological tests are often cited to show that humans are fundamentally irrational. I argue that even the most menacing ideological juggernauts such as Communism, National Socialism and various Fundamentalisms can be undermined by sound argument. Rationality does not mean the absence of error, but the possibility of correcting error in the light of criticism. In this sense, all human beliefs are rational: they are all vulnerable to being abandoned when shown to be faulty. The book is Published by Open Court Publishers, Chicago and available from many outlets, including the U.S. and U.K. Amazon sites.

Nominated by

Voting Available until 28th February 2013.

Reached No.56 in Best Sellers (on in the category: Philosophy/Criticism.)


"At last, a philosopher in the 21st century willing to stand up and argue for the power of sheer human rationality. Because Ray Percival is so convinced, correctly, of the impact of a rational argument on the human intellect, he is unafraid to offer a no holds barred, comprehensive brief on the strength of rationality in this book. Preferring Kant to cant, surveying history and reason from Socrates to today's age of terrorism, Percival has written a tract that Milton, Jefferson, Mill, and Karl Popper would be proud of. The next time I get into an argument with a well-meaning person who wishes to censor a propagandistic, corporate, or individually hateful point of view, I will recommend a reading of Percival's The Myth of the Closed Mind."

-Paul Levinson, Professor of Communication and Media Studies (Fordham University) and author of New New Media.

“Ray Percival calls his own view outrageous, and it does indeed outrage the sensibilities of today’s shallow and fashionable intellectuals, who continually bleat about human irrationality. But even those already disposed to agree with Percival and Aristotle that humans are rational animals will still be repeatedly surprised by the many delightful, witty, and profound insights in The Myth of the Closed Mind. How much better to have written one classic work than a hundred meretricious potboilers. If he were henceforth to write nothing else, Professor Percival has his classic.”

—J.C. Lester, author of Escape from Leviathan

“Some of what Percival claims is outrageous but some of it is not. Even though he may not convince most of his readers, many of his arguments are both ingenious and entertaining—and often point to unresolved issues in the theory of rationality.”

—James Fetzer, author of The Evolution of Intelligence and Render Unto Darwin

Available from online bookstores:

Available from Open Court:

Also available as a Kindle eBook and as an Ibook at the U.S.A. Apple Store.

Malachi Hacohen and Barry McMullin panel on Karl Popper

Panel interview by Dan Schneider for Cosmoetica, 2nd July 2017.

The Aims of
The Karl Popper Web

  1. Promote, explore and defend the heroic and critical ethos of science through philosophical debate.

  2. Promote the sense of wonder that forms the motivation for science and philosophy.

  3. Critically explore and apply the work of Sir Karl Popper, a key figure in the defence of science.

  4. Make this accessible to new audiences and participants: beginners to science and philosophy, the newly opened societies of Russia, Eastern and Central Europe, less developed countries, the young and the disabled.

Karl Popper's 1934 Bombshell

In 1934 Popper published what many regard as his Magnum Opus The Logic of Scientific Discovery. The famous chemist Wachtershauser said that this is a "gem" and that it liberated him from a sterile accounting view of science. Wachtershauser subsequently went on to develop one of the main theories of the origin of life. Frank Tipler, the famous cosmologist, regards this as the most important book of the 20th century. In one majestic and systematic attack, psychologism, naturalism, inductionism, and logical positivism are swept away and replaced by a set of methodological rules called Falsificationism. Falsificationism is the idea that science advances by unjustified, exaggerated guesses followed by unstinting criticism. Only hypotheses capable of clashing with observation reports are allowed to count as scientific. "Gold is soluble in hydrochloric acid" is scientific (though false); "Some homeopathic medicine does work" is, taken on its own, unscientific (though possibly true). The first is scientific because we can eliminate it if it is false; the second is unscientific because even if it were false we could not get rid of it by confronting it with an observation report that contradicted it. Unfalsifiable theories are like the computer programs with no uninstall option that just clog up the computer's precious storage space. Falsifiable theories, on the other hand, enhance our control over error while expanding the richness of what we can say about the world.

Any "positive support" for theories is both unobtainable and superfluous; all we can and need do is create theories and eliminate error - and even this is hypothetical, though often successful. Many superficial commentaries are keen to point out that other people stressed the importance of seeking refutations before Popper. They overlook the fact that Popper was the first to argue that this is sufficient.

This idea of conjecture and refutation is elaborated with an orchestration suggestive of someone who loves great music. (Popper loved Mozart and Bach, and took great pleasure in composing his own music.) The common idea that Popper neglected to consider whether Falsificationism itself is falsifiable is already scotched here. You can falsify a description, but not a rule of method as such (though obviously a rule can be criticized in other ways). The notion that science offers proof is now only advanced by popular treatments of science on TV and in (many) newspapers - most journalists (with a few important exceptions) are sadly completely devoid of theoretical knowledge: a side-effect of overspecializing on the immediate moment. But then, anyone can improve!

Most people who think they have a ready rebuff to Popper's position have never read his work. If they only read the original works, in most cases they would see that their supposed "Point that Popper neglected" had already been considered and exploded. A good example of this is Lewis Wolpert's remarks on Popper's works in his otherwise excellent book The Unnatural Nature of Science. He seems to think that Popper's falsifiability criterion ignores hypotheses about probabilities - overlooking the blatant fact that The Logic of Scientific Discovery devotes more than a third of its pages to the two fundamental problems of probability in an effort to find a solution that will also allow hypotheses about the probability of events to be capable of clashing with the evidence! Popper was in fact fascinated by probability and even produced his own axiomatisation of the probability calculus.

thumbnail picture of book

For the best current re-statement, defence and - more importantly - application of Falsificationism see David Miller's Critical Rationalism: A Re-Statement and Defence..(for (for Miller was a very close friend and colleague of Popper's. He pulls no punches and is (despite his modesty) Popper's best knight. If you want razor-sharp logical accuracy, a full arsenal of arguments, and comprehensive demolition (with unrestrained collateral damage) of the opposition, Miller's book is the answer. It is important for students because it carefully delineates the various relevant intellectual combatants. And will interest scientists because of its treatment of chaos and propensities. 

For more on Miller's important work, see his website:


Feel free to join our discussion group,Critical Cafe, and visit the Book Shop for my abstracts on Popper's books. In our forums we have the pleasure of the company of both critics and adherents of Popper's work. This makes for lively and productive exchanges. Join us in our intellectual quest.


Featured Books:

David Miller:

Out Of Error: Further Essays On Critical Rationalism (January 2006. Ashgate Pub Co.)

A Review by Kenneth Allan Hopf from Amazon:

 For at least a year now this book has been my constant companion. Every one of the essays bears reading again and again. If you want the purest crystalline critical rationalism, this is the book you must read. The last vestiges of justificationism are gone. What is left is a thing of beauty and rare insight. I'm not going to try to summarize any of the essays because anything I could say would just be a pale reflection. What I will say is that Miller's formulations are strikingly original, really unlike any of Popper's other students. And the logical rigor is there in some ways even more than with Popper.



New Paperback Edition: (26 April 2012. The University of Buckingham Press.)

Escape From Leviathan: Libertarianism Without Justificationism

Lester's book is a fascinating application of Karl Popper's method of critical rationalism to the elaboration and defense of a conjectural utopia. Lester's book makes anarchy a more appealing type of society by dealing with a central concern of many intellectuals: reconciling the apparently incompatible goals of liberty, welfare and the absence of government. This edition is only £14.24. At that price and with such critical acclaim, any library on liberty without it would be shamefully incomplete. I'm putting in an order right now.

A sample of the critical acclaim for Lester's book:

Lester's book develops a sustained and at times fresh and surprising argument for its compatibility conclusions. It constitutes a formidable intellectual challenge to the social democratic establishment in Political theory.' Professor Antony Flew 'Lester argues that utility is compatible with liberty, understood in its classically 'negative' sense. In the process, he has written a remarkable book, informed by a masterly knowledge of economics and filled with careful analytical detail. He deals with a vast range of criticisms, and in the process undoes a great deal of theoretical mischief on the relations between these important concepts, including much by philosophers of major reputation. His accounts of instrumental rationality, of property rights, of public goods problems, and of restitution for criminal cases, are important contributions and will be discussed with interest for long. Few among us will fail to benefit from reading it.' - Professor Jan Narveson

This book probably represents a landmark in the literature of liberalism on two counts. One of these is the robust statement of his major thesis on the compatibility of free markets, liberty and welfare. The other is the way he uses the non-authoritarian theory of rationality expounded by Karl Popper and William W Bartley. Rafe Champion.

David Barker'sWelcome to Free America. (26 October 2011)

image of the book: Welcome to Free America

David Barker invites us to join him in a captivating thought experiment about a possible future without the united states government. Starting with a clear history and diagnosis of the grave and incorrigible economic crisis that haunts the u.s. government - a colossal and unstoppable debt produced by the contradictory demands of voters for lower taxes and more government spending - David Barker predicts the collapse of government and its replacement by a thriving society based on rules without rulers. Driven by the unpopularity of higher taxes and cut backs in government spending, competing political parties learn to take refuge in the less visible tactics of printing money and increasing government borrowing. But the unintended affect of this is an eventual inability of the government to pay its bills, at which point the u.s. government collapses along with the authority of government. Drawing on his specialization in economics, David Barker suggests ingenious and plausible ways in which social problems in a society without government can be solved while respecting justice and liberty. Of course, as Karl Popper argued, because of the influence of new knowledge in the future, there is no inevitability in the movement of society and we cannot give strictly a "scientific" prediction of a detailed future. But we can make educated guesses about it and even about our personal utopia (in the sense of ideal society). It could work, but even if it wouldn't work with those particular arrangements, Barker's hypothetical future can help us to view our current state of affairs more clearly. After all, we only have governments and collusions between governments and business as examples. We don't have true purely private property markets - yet.


David Deutsch

The Beginning of Infinity. (21 July 2011. Adult Viking.)

The Beginning of Infinity

David Deutsch is an admirer of Karl Popper's work and he applies Popper's and a host of his own keen insights with a clarity worthy of Bertrand Russell. One of my pet delights of the book is that drawing on his reflections as a pioneer of science (David was the inventor of the concept of the quantum computer), David squashes the silly but popular notion that science is about the prediction of experiences. Except for pyschology, of course, scientific theories actually do not talk about experiences as such, but rather about the underlying universal structures of the world. In contrast to the mass media's cacophony of doomsday prophecies, Deutsch's The Beginning of Infinity espouses a refreshingly optimistic view of humanity's potential for everlasting progress in the growth of knowledge, morality and the extension of our increasingly richer lives.


Bold ... profound ... provocative and persuasive. The Economist Science has never had an advocate quite like David Deutsch. He is a computational physicist on a par with his touchstones Alan Turing and Richard Feynman, and also a philosopher in the line of his greatest hero, Karl Popper. His arguments are so clear that to read him is to experience the thrill of the highest level of discourse available on this planet and to understand it ...This is the great Life, the Universe and Everything book for our time and the answer is not 42: it is infinity. To understand precisely what Deutsch means by this, you will have to read him. Do so and lose your parochial blinkers forever. -- Peter Forbes The Independent



Latest Books by or on Popper:

 The Two Fundamental Problems of the Theory of Knowledge

Karl Popper. (26 November 2008. Routledge.)

In a letter of 1932, Karl Popper described Die beiden Grundprobleme der Erkenntnistheorie – The Two Fundamental Problems of the Theory of Knowledge – as ‘…a child of crises, above all of …the crisis of physics.’
Finally available in English, it is a major contribution to the philosophy of science, epistemology and twentieth century philosophy generally.
The two fundamental problems of knowledge that lie at the centre of the book are the problem of induction, that although we are able to observe only a limited number of particular events, science nevertheless advances unrestricted universal statements; and the problem of demarcation, which asks for a separating line between empirical science and non-science. Popper seeks to solve these two basic problems with his celebrated theory of falsifiability, arguing that the inferences made in science are not inductive but deductive; science does not start with observations and proceed to generalise them but with problems, which it attacks with bold conjectures.
The Two Fundamental Problems of the Theory of Knowledge is essential reading for anyone interested in Karl Popper, in the history and philosophy of science, and in the methods and theories of science itself. 

After The Open Society: Selected Social and Political Writings. 


Editors: Jeremy Shearmur and Piers Norris Turner.  (14 May 2008.)

In this long-awaited volume, Jeremy Shearmur and Piers Norris Turner bring to light Popper's most important unpublished and uncollected writings from the time of The Open Society until his death in 1994. After The Open Society: Selected Social and Political Writings reveals the development of Popper's political and philosophical thought during and after the Second World War, from his early socialism through to the radical humanitarianism of The Open Society. The papers in this collection, many of which are available here for the first time, demonstrate the clarity and pertinence of Popper's thinking on such topics as religion, history, Plato and Aristotle, while revealing a lifetime of unwavering political commitment. After The Open Society illuminates the thought of one of the twentieth century's greatest philosophers and is essential reading for anyone interested in the recent course of philosophy, politics, history and society.  

Karl R. Popper: Fruhe Schriften

by Troels Eggers Hansen (31 December 2006)


Background to The Karl Popper Web

The Karl Popper Web is an online complement to the Annual Conference on the Philosophy of Sir Karl Popper. I announced my intention to set up such a service at the 1995 Conference held at the LSE on 11th March. At the Conference I was approached by Barry McMullin, of the School of Electronic Engineering of Dublin City University, who offered his help to put together an electronic forum on the Internet.

Audience and Participants

Apart from perhaps Bertrand Russell, Popper is unique in having had such a wide influence outside of traditional academia. Many people, not just philosophers, have been intrigued, inspired or annoyed by Popper's ideas. His ideas have relevance and impact in science, business, politics, art, music, and also in peoples' personal lives. We expect and encourage both professional and non-professional philosophers to participate in or visit The Karl Popper Web. Professionals and non-professionals can learn from one another. The good habits of the professional (diligence, focus etc.) can rub off and the professional is saved from the obscurity and elitism of overspecializing by having to be clear to the non-professional. The great philosophy and science writers (Darwin, Russell, Popper, Einstein, Dawkins, Deutsch) are all characterized by their keenness to communicate to all intelligent people, not simply to their co-specialists. TKPW is a globally accessible space for the meeting of minds from different backgrounds and specialisms with a common sense of wonder in life and the world.

The Portrayal of Science

Many projects intended to promote a better understanding of science are very clever but also in way superficial. They portray the effects of scientific laws - the fireworks of science - very well, but alone they cannot convey and inspire the method and the self-critical ethos of science. I am in favor of firework displays, and the laws of science need well-designed and innovative illustration. As Lewis Wolpert's book argues superbly, science is not technology. It is not computers, Saturn V rockets, fission or fusion reactors, nor any of the exciting and fascinating products of an advanced industrial society that enable us to control the world. It is rather a desire to understand the world. This is Wolpert's common ground with Popper. I wish to emphasise the philosophical aspects of science, which spring from a wonder at the existence, structure and evolution of the world.

For an excellent defense of the deeper poetic quest of science, see Richard Dawkins's book, Unweaving The Rainbow. Dawkins, the Charles Simonyi Professor of the Public Understanding of Science at Oxford University, and author of The Selfish Gene, shows that when science solves its puzzles we find deeper mysteries. He also shows how our appetite for wonder can be lead astray into the dead ends of supernaturalism, which relies on savoring but not solving mysteries. When science succeeds we always get both the wonderful revelation plus further helpings of the mysterious. You can have your cake and eat it! Unweaving the Rainbow. (for (for



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