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Introduction: The Sources of Knowledge and of  Ignorance

"The traditional systems of epistemology may be said to result from yes-answers and no-answers to questions about the sources of our knowledge. They never challenge these questions, or dispute their legitimacy; the questions are taken as perfectly natural, and nobody seems to see any harm in them. This is quite interesting, for these questions are clearly authoritarian in spirit."

Conjectures and Refutations is a collection of Popper’s papers that appeared in 1963, shortly after The Logic of Scientific Discovery (1959) and a long time after The Open Society and its Enemies (1945). OSE achieved the status of a banned book in some leftwing circles, and possibly in some conservative circles as well on account of the criticism of Plato.

The Introduction is a pivotal piece because it pinpointed the authoritarian structure of Western thought. It exerted a great deal of influence on William W Bartley who became one of Popper's best expositors, partly on account of the message that he picked up from this paper. He actually heard it live when it was delivered as the Annual Philosophical Lecture read before the British Academy in 1960.

The paper 'On the sources of knowledge and of ignorance' provides some important insights into the structure of thinking that is embedded in traditional philosophy, especially the authoritarian element that has really important consequences in politics.

The paper contains seventeen sections after a short introduction.

Empiricism and Rationalism

"The problem which I wish to examine afresh in this lecture...may perhaps be described as an aspect of the old quarrel between the British and the Continental schools of philosophy - the quarrel between the classical empiricism of Bacon, Locke, Berkeley, Hume and Mill, and the classical rationalism or intellectualism of Descartes, Spinoza and Leibniz. In this quarrel the British school insisted that the ultimate source of all knowledge was observation, while the Continental school insisted that it was the intellectual intuition of clear and distinct ideas."

"Most of these issues are still very much alive. Not only has empiricism, still the ruling doctrine in England, conquered the United States, but it is now widely accepted, on the European Continent, as the true theory of scientific knowledge. Cartesian intellectualism, alas, has been only too often distorted into one or other of the various forms of modern irrationalism. In this lecture I shall try to show of the two schools of empiricism and rationalism that their differences are much smaller than their similarities, and that both are mistaken. I hold that they are mistaken although I am myself an empiricist and a rationalist of sorts. But I believe that, though observation and reason each have an important role to play, these roles hardly resemble those which their classical defenders attributed to them. More especially, I shall try to show that neither observation nor reason can be described as a source of knowledge, in the sense that they have been claimed to be sources of knowledge, down to the present day."


In this section Popper noted the important and helpful function of the doctrine that "truth is manifest", while he also warned of the downside of such an optimistic but false idea.

"The great movement of liberation that started in the Renaissance and led through the many vicissitudes of the reformation and the religious and revolutionary wars to the free societies in which the English-speaking people are privileged to live, this movement was inspired throughout by an unparalleled epistemologial optimism: by a most optimistic view of man's power to discern truth and to acquire knowledge."

At the heart of this new optimistic view of the possibility of knowledge lies the doctrine that truth is manifest.Chief among the standard bearers of this idea were Bacon and Descartes, and it inspired the birth of modern science and technology which has done so much to emancipate people from ignorance, from political despotisms and also from want and poverty.


In this short section Popper noted that even an abstract study like epistemology can be motivated, even unconsciously, by political hopes and dreams. He suggested that this should be a warning to us. But what can we do about it?

He confessed to being a liberal, in the English, non-collectivist sense. And he wrote "I feel that few things are more important for a liberal than to submit the various theories of liberalism to a searching critical examination". He found that many of the ideas and doctrines which had inspired political liberals are not tenable, including the doctrine of the manifest truth and the inevitability of progress.

V and VI

In the course of Popper's examination of the ideas that underpinned liberalism, alongside the "manifest truth" theory he encountered what he called "the conspiracy theory of ignorance". The two are connected because if the truth is manifest to honest and clear-eyed seekers, then if they fall into error, or promulgate it, then either their motivation is suspect or they have been taken in and deluded or led astray by some other evil person or group.

"This false epistemology was the major inspiration of an intellectual and moral revolution without parallel in history. It encouraged men to think for themselves. It gave them hope that through knowledge they might free themselves and others from servitude and misery. It made modern science possible. It became the basis of the fight against censorship and the suppression of free thought... It made men feel responsible for themselves and for others, and eager to improve not only their own condition but also that of their fellow men."

"It is a case of a bad idea inspiring many good ones. This false epistemology, however, has also led to disastrous consequences. The theory that truth is manifest - that it is there for everyone to see, if only he wants to see it - this theory is the basis of almost every kind of fanaticism. For only the most depraved wickedness can refuse to see the manifest truth; only those who have reason to fear truth conspire to suppress it."


In these sections Popper examined the historical roots of optimistic and pessimistic epistemologies, from Plato to Bacon and Descartes, with some space devoted to the quest for the truth of statements in their origin and also the pursuit of the true meaning of terms (essentialism). I will not dwell on the material in these sections but will return to the main topic of the paper.


"I will now leave all these largely historical reflections aside, and turn to the problems themselves, and to their solution".

The whole of this section is on line.

This section of the lecture is an attack on empiricism, that is, the doctrine that knowledge has to rest on the firm foundations of observation, that is, facts that have been presented to the senses or have lodged in the memory after entering by way of the senses.

According to this doctrine, "if we make an assertion, we must justify it," but this means that we must be able to answer the following questions: 'How do you know? What are the sources of your assertion?'

The counter-argument is that we usually do not make assertions based on immediate obervations of the events in question, the more usual sources are things like newspaper or Encyclopedia Britannica, a lecture, a textbook or a journal article.

The empiricist replies that nevertheless the basis of the reports in the secondary sources are observations, otherwise the reports might be classified as poetry, fiction or even lies.

The gist of Popper's argument at this point is that the usual method of checking reports is not to investigate into the source which could result in an infinite regress to check each stage of the transmission of the information, but rather to seek corroborating information from another source or in science to repeat a critical experiment to ensure that the same result can be obtained in different laboratories.

"The most striking thing about the observationalist program of asking for sources - apart from its tediousness - is its stark violation of commonsense. For if we are in doubt about an observation, then the normal procedure is to test it, rather than to ask for its sources; and if we find independent corroboration, then we shall often accept the assertion without bothering at all about the source."

However that is not always the case and there are occasions when it is important to ascertain the source, where some sources are known to be better than others (though none can be regarded as infallible). Another situation where sources do have to be checked is historical research.

"Testing an historical assertion always means going back to sources; but not, as a rule, to the reports of eyewitnesses".


In this short section Popper sums up his view that there are many sources of knowledge but none have authority.


The authoritarian structure of traditional philosophy

"The traditional systems of epistemology may be said to result from yes-answers and no-answers to questions about the sources of our knowledge. They never challenge these questions, or dispute their legitimacy; the questions are taken as perfectly natural, and nobody seems to see any harm in them. This is quite interesting, for these questions are clearly authoritarian in spirit. They can be compared with the traditional questions of political theory, 'Who should rule?' which begs for an authoritarian answer such as 'the best', or 'the wisest' or 'the people', or 'the majority'. (It suggests, incidentally, such silly alternatives as 'Who should be our rulers: the capitalists or the workers?', analogous to 'What is the ultimate source of knowledge, the intellect or the senses?'). "

This political question is wrongly put and the answers which is illicits are paradoxical (Chapter 7 of OSE). It should be replaced by a completely different question such as 'How can we organise our political institutions so that bad or incompetent rulers cannot do too much damage?' The question about the sources of our knowledge can be replaced in a similar way.

The alternative that Popper suggested is the question of detecting and eliminating error, by means of critical appraisal by all the methods of criticism that we can muster - logical analysis, experimental testing, consistency with other theories etc.


This section is on line. Popper spells ten theses to summarise the results of the discussion in the lecture.

1. There are no ultimate sources of knowledge. Every source, every suggestion, is welcome; and every source, every suggestion, is open to critical examination. Except in history, we usually examine the facts themselves rather than the sources of our information.

10. Every solution to a problem raises new unsolved problems; the more so the deeper the original problem and the bolder its solution.


The final section makes a case to give up the quest for the conclusive justification of our knowledge, but not to abandon the idea of truth as the goal of investigation. Some who accept that knowledge is essentially fallible abandon the quest for truth or opt for arbitrary authorities. Popper followed Russell in the belief that no person can establish the truth by decree, instead we should accept that truth is above human authority.

Bill Bartley on the structure of Popper's epistemology.

The importance of Bartley's take on Popper was exemplified by my own experience in a series of lectures to an elderly group of people who convened to discuss the Philosophy of Humanism. They met for an afternoon every two weeks over a period of ten years and they covered a huge amount of ground although they never produced anything that aroused much interest from the committee of the local Humanist Society or the membership at large. I led the discussion fairly regularly for about a year, late in the 10-year period and a very interesting pattern emerged.

After about four sessions the group seemed to be getting the idea of Popper's theory of conjectural knowledge, then they decided to invite some other discussion leader (a professional philosopher) just for variety. When I returned I had to start all over again to get across the idea of conjectural knowledge and the criticism of induction. Then the same process occurred, they made good progress with Popper's views on knowledge and some other issues like essentialism, then they had a session or two with other discussion leaders and when I came back, the process had to start from the beginning again.

This was reminiscent of the mythical figure of Sisyphus who pushed a stone up hill all day and it rolled back down to the bottom during the night. Then I decided to move backwards or sideways and so I fed them some papers by Bill Bartley. Most of the group members were keen enough to undertake quite serious reading, even though they often struggled with the interpretation. They certainly struggled with Bartley but two of them stuck to the task and as a result they never rolled back down the hill again. Some of the Bartley articles are now on line.

The point of that story is that Bartley explained something about the structure of Popper's ideas that is rendered invisible by the more common approaches to the theory of knowledge and belief, especially the aim of justification or confirmation of beliefs. When the difference in structure is grasped, it is much harder (though by no means impossible) for people to lose the plot and revert back to the conventional ways. For academic philosophers of course the situation is complicated by the need to maintain credibility in the profession in order to achieve tenure and promotion.

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Conjectures and Refutations
Karl Popper