The Limits of Toleration

What did Karl Popper really think about tolerance and intolerance?

Over the past few years, a cartoon has been doing the rounds on social media. It depicts the philosopher Karl Popper laying out his ‘paradox of tolerance.’ The cartoon is based on a long endnote in Popper’s great work The Open Society and its Enemies (which was written in New Zealand), and on this paragraph in particular:

Less well known is the paradox of tolerance: unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them. In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise. But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law, and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal (OS I, 265).

For the most part the text of the cartoon simply paraphrases sections of this paragraph (Popper’s ‘we should claim that any movement preaching intolerance places itself outside the law’ becomes ‘any movement that preaches intolerance and persecution must be outside the law,’ for example). But it also leaves out two sentences (running from ‘In this formulation’ to ‘fists or pistols’), which suggest that the intolerant should be suppressed only when they resort to violence rather than argument. Though this has been widely pointed out, Popper continues to be cited (including in this country) in support of the view that we should clamp down on intolerance even when it stops short of violence. 

Popper’s cartoon has taken on something of a life of its own on the internet, with counter-cartoons replacing Nazis with Islamists, anti-capitalists, or even Chinese communists. But the many blog posts and think-pieces that purport to show what Popper really thought about tolerance and intolerance rarely look beyond the paragraph we’ve quoted above, and almost never venture beyond the first volume of The Open Society and its Enemies. 

In this piece, we draw on a wider range of Popper’s writings, including personal letters, to shed more light on what the philosopher’s views on toleration actually were. As we shall see, Popper’s views on this topic hardly constitute a fully thought-out theory. Where exactly we should set the limits of toleration in speech and action is still very much a question that citizens of contemporary societies will have to answer for themselves. At the same time, Popper’s thinking about tolerance does offer some guidance about where we should draw the lines around toleration. 

What did Popper actually say about tolerance?

Much of what Popper had to say about tolerance was written simply in support of toleration in general, as a feature of the ‘open societies’ he wished to promote. On the most general level, Popper saw tolerance as a necessary condition for the kind of pluralism that any liberal society would have to accommodate. As he put it in a 1945 letter to the Australian neurophysiologist John Eccles, ‘We must build a world in which different creeds, different religious and different moral creeds, must be able to live together in peace’; to this end, ‘a common denominator’ was needed ‘such as tolerance of everybody who is prepared to tolerate’. ‘Democracy will tolerate everyone except the intolerant,’ the University of Canterbury student magazine CANTA reported ‘Dr. Popper’ as saying, as ‘the right to be different is of fundamental importance.’ By the same token, open societies should ‘avoid imposing any particular social philosophy on people’ and ‘give people a chance to choose’ between different values.

Popper sometimes saw tolerance as something that flowed naturally from a recognition of our fallibility as human beings. Popper was fond of quoting the first line of Voltaire’s entry on tolerance in his Philosophical Dictionary (1764), which runs (to use Popper’s own translation), ‘What is tolerance? It is a necessary consequence of our humanity. We are all fallible, and prone to error. Let us then pardon each other’s follies’ (CR, 8; ATOS, 314).

Unsurprisingly, Popper often linked this general human quality of fallibility with his more specific theory of fallibilism, which emphasized the uncertainty of even our best knowledge and the importance of being open to different views – while also leaving all views open to criticism. Rationalism, he writes in the second volume of The Open Society, ‘is bound up with the idea that everybody is liable to make mistakes’ and therefore ‘with the idea that the other fellow has a right to be heard’; it thus implies ‘the recognition of the claim to tolerance, at least of all those who are not intolerant themselves’ (OS II, 238). A more concise formulation of this view can be found in a 1973 letter: ‘This fallibilism’ (that is, scientific or rational fallibilism) ‘has important moral consequences; tolerance is one of them’.

If toleration, for Popper, goes hand in hand with a scientific mindset, it is also an enemy to (and perhaps an antidote for) any notion that one’s ideas are specially favoured, either by the ‘historical inevitability’ of a particular worldview; or, indeed, by divine sanction. Popper warned against simply dismissing certain views as ‘outdated,’ a term that, as he told the humanist Paul Kurtz in a 1973 letter, he viewed as itself outdated. And in a 1981 letter to a Professor Stubbins he condemned Luther’s 1525 On the Bondage of the Will as ‘essentially directed against toleration, against non-violence and peace, and for the implied thesis that he is God’s instrument – that his words are The Word of God.’

This kind of millenarian certainty aside, Popper saw religious views as entitled to a certain level of toleration. ‘We must be tolerant,’ as he put it in a 1971 letter to the French biochemist Jacques Monod, ‘even towards what we regard as a basically dangerous lie.’ ‘And we should be seriously tolerant,’ he added in a 1980 letter to Kurtz, ‘of anyone who honestly expresses religious views.’ Indeed, he had written to Kurtz in his earlier letter, ‘we should not only declare but show our own tolerance towards tolerant religion and tolerant ideologies.’ 

Popper stressed that critical rationalists in particular should try to practice this kind of religious tolerance. He agreed with Paul Kurtz and Edwin H. Wilson’s second Humanist Manifesto (1973), he wrote them, that ‘we must not become dogmatic and churchlike ourselves.’ In a 1946 essay he wrote that, ‘a tolerant society must tolerate…irrationalism, as long as it is not an aggressively intolerant brand of irrationalism’ (ATOS, 136). And in another essay written two years later, Popper reasoned that while a ‘strongly emotional intolerance’ seemed to be ‘characteristic of all traditionalism,’ what critical rationalists should seek to do was to ‘replace the intolerance of the traditionalists with a new tradition – the tradition of tolerance’ (CR, 132).

Can democracy tolerate the intolerant?

What did Popper mean by ‘democracy will tolerate everyone except the intolerant’ and other variations on the ‘paradox of tolerance’? One clue is provided in a sentence we’ve just quoted, where Popper states that we should tolerate all irrationalism that isn’t ‘aggressively intolerant’ (our emphasis).  In a 1963 lecture on ‘The Open Society and the Democratic State,’ Popper spoke about people ‘who preach intolerance and who, at the same time, accuse the tolerant of hypocrisy, because they’ – the tolerant – ‘are not prepared to tolerate every aggressive form of intolerance’ (ATOS, 240).  Note the importance of aggression, something that Popper underlined in his 1973 letter to Kurtz: ‘we must not behave aggressively towards views and towards people who have other views than we have,’ he wrote, ‘provided that they are not aggressive.’

It’s not completely clear what Popper means by ‘aggression’ here – does the ‘they’ in that last phrase refer to people or to views? – but the fact Popper says that we must not behave aggressively makes it likely that what he had in mind wasn’t simply an aggressive argument or tone of voice, but aggressive actions – that is, something close to, or even identical with, coercion or violence. 

Other evidence points towards the conclusion that Popper’s main worry was coercive violence. Popper often said something to the effect that we should recognize ‘the claim to tolerance, at least of all those who are not intolerant themselves’. There’s an appeal to reciprocity here, an appeal that Popper occasionally made more explicit. ‘Voltaire saw very clearly,’ Popper wrote in his 1981 essay ‘On Toleration,’ that ‘toleration must be mutual: that it is based on reciprocity’ (ATOS, 314).  In his 1963 lecture ‘The Open Society and the Democratic State,’ Popper reiterated that ‘there can be no obligation upon the tolerant to tolerate the intolerant,’ and added that he had in mind ‘those who do not reciprocate’ (ATOS, 239).  

But what did not reciprocating tolerance look like exactly? In ‘On Toleration,’ Popper spoke of minorities ‘who are unwilling to reciprocate the tolerance offered to them by the majority: minorities who accept a principle of intolerance; who accept a theory of the necessity of violence and who may even act violently.’ Later in the same essay he wrote that ‘toleration can only exist on a basis of mutuality,’ and that ‘our duty to tolerate such a minority ends when the minority begins to act violently’ (ATOS, 315).  In ‘The Open Society and the Democratic State,’ he argued that ‘though we should guarantee freedom of opinion to all those who are prepared to reciprocate, we must not include in this guarantee those who seriously propagate intolerance or violence’ – and here ‘or violence’ seems less to present an alternative than to explain what he means by ‘intolerance.’ Something similar seems to be going on in ‘On Toleration’ when he speaks of ‘intolerant ideologies: ideologies that entail the principle that all who dissent from them must be suppressed by force’ (ATOS, 313). 

In ‘On Toleration’ Popper does also write that ‘our exaggerated fear that we who are for toleration might ourselves become intolerant has led to the mistaken and dangerous attitude that we must tolerate everything, perhaps even acts of violence; but certainly anything that falls short of an act of violence’ (ATOS, 314). Does this imply some skepticism about the idea that everything short of violence should be tolerated? 

In our view, Popper probably means that movements that make very credible threats of violence might also be criminalized, even if they have not yet committed ‘an act of violence’ (and here we might recall of his mention, in ‘On Toleration,’ of minorities ‘who may even act violently,’ and his warning that our duty to tolerance ends ‘when the minority begins to actviolently’ – our emphasis; ATOS, 315). Later on in ‘On Toleration,’ Popper says that ‘we need not tolerate even the threat of intolerance; and we must not tolerate it if the threat is getting serious’ (ATOS, 315) – by which he seems to mean intolerance that has become violent, or clearly threatens to.

This focus on violence as the key criterion for reciprocal intolerance on the part of the state is something that Popper reiterates on a number of occasions, especially in his paper on the open society and the democratic state. He reiterates the point with some lively examples, starting with a story about tigers. ‘I once read a touching story of a community which lived in the Indian jungle, and which disappeared because of its belief in the holiness of life, including that of tigers,’ he told the essay’s original audience in Delhi. ‘Unfortunately the tigers did not reciprocate.’

Popper’s other example in this lecture was a more serious one: ‘the German republic before 1933 – the so-called Weimar Republic – tolerated Hitler; but Hitler did not reciprocate’ (ATOS, 239). If the cartoon we began this piece with gets one thing right, it was that Popper’s thinking about intolerance was profoundly marked by his experience as someone of Jewish origin (although raised as Lutheran) who escaped the looming shadow of Hitler in 1937.  

At the same time, Popper’s Open Society would be an excoriation of – and a warning against – both the great totalitarianisms of the twentieth century: Fascism and Communism. In a crucial passage in ‘On Toleration,’ Popper described the impact of both these movements on his thinking from his brief period as a young socialist on:

I shall never forget how often I heard it asserted, especially in 1918 and 1919, that ‘capitalism’ claims more victims of its violence on every single day than the whole social revolution will ever claim. And I shall never forget that I actually believed this myth for a number or weeks before I was 17 years old, and before I had seen some of the victims of the social revolution. This was an experience which made me for ever highly critical of all such claims, and of all excuses for using violence, from whatever side. I changed my mind somewhat when Goering, after the Nazis had come to power by a majority vote, declared that he would personally back any stormtrooper who was using violence against anybody even if he made a little mistake and got the wrong person. Then came the famous ‘Night of the Long Knives’ — which is what the Nazis called it in advance. This was the night when they used their long knives and their pistols and their rifles…After these events in Germany, I gave up my absolute commitment to non-violence: I realized that there was a limit to toleration (ATOS, 316).

Violence matters

Note again the focus on violence, with the Nazis’ ‘long knives and pistols and rifles’ here expanding on the ‘fists or pistols’ of the endnote in The Open Society. It is violence that finally made the young Popper recognize that there are limits to tolerance: not hurtful speech, not the rabid antisemitism of 1930s Vienna, and not even the overthrow of German (and Austrian) democracy. 

And in fact, even when Popper’s focus was primarily on democracy, it is still arguably violence that is, in the final analysis, his real concern. Earlier in the same essay, Popper talked about ‘a party that conspires – perhaps partly openly, or quite secretly – to abolish democracy’; ‘to such a party,’ he says, ‘we must not submit, even if it has gained a majority.’ As in the passage above, the reference is to the German elections of July 1932, in which the National Socialists had won a simple majority; but here Popper makes clear that his over-riding fear is that ‘the abolition of democracy will lead…to arbitrary action, and to violence’ (ATOS, 315).

Such fears accord with Popper’s theory of democracy, according to which democracy is simply the type of government ‘of which we can get rid without bloodshed’ (OS II, 124). The main point of democracy, in other words, is simply to enable us to change our government without violence. Similarly, the main point of toleration for Popper seems to have been to allow individuals to pursue their own interests and live their own lives without coercive interference.

But if practising toleration is a reciprocal affair (we should tolerate others who are willing to tolerate us in turn), so is policing its boundaries. This is why Popper, in the crucial autobiographical passage quoted above, tells us, in the same breath, that the Nazis’ violence led him both to give up his ‘absolute commitment to non-violence’ and to realize that there was ‘a limit to toleration.’ To spell out the implications of this in full, what Popper is saying is that a liberal democratic state is justified in using coercion against those who threaten it, or its citizens, with violence.

In a 2019 piece in The Dominion Post, journalist Will Harvie revisited the crucial footnote in The Open Society that we began with to argue that Popper wasn’t, in fact, concerned solely with violence – with those that resorted to ‘fists or pistols’ in response to arguments. Harvie emphasized the endnote’s final sentence, in which Popper says that ‘we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.’ Harvie concludes that ‘it’s not just violence’ that Popper would have banned; ‘it’s incitement.’

Harvie is clearly correct that Popper advocates criminalizing incitement to violence. But we should note that the three types of violence Popper mentions in this connection – murder, kidnapping, and slavery – are rather egregious ones. And we should also notice, once again, what Popper stops short of recommending. He doesn’t recommend a ban on speech that is grossly offensive, ‘harmful,’ or even that might constitute ‘group libel’ (the New Zealand legal philosopher Jeremy Waldron’s conception of ‘hate speech’). 

In fact, everything we know suggests Popper would have been strongly against this narrower view of the limits of toleration. He himself, remember, privately conceded to more zealous rationalists that religion might well be ‘a dangerous lie,’ and yet he repeatedly argued not only that we should tolerate religious views, but even that we should accord them a certain measure of respect. This makes it extremely unlikely that he would have endorsed the idea that certain opinions should be censored or ‘de-platformed’ for causing ‘hurt,’ ‘dismay’ or ‘harm’ (to use some terms that have been in frequent use in recent debates about free speech in this country). 

In fact, Popper wrote in a 1980 letter to Kurtz that even ‘those aspects of religions and other institutions, which openly subscribe to intolerance, are, perhaps, best fought by a respect for and tolerance of those aspects, which are not intolerant, even though we may not agree with their views or sympathise with their practices’. In other words, whenever possible, we should try to counter even clearly intolerant views by tolerance and reason. Popper tried to make this clear in the endnote on the ‘paradox of tolerance’ that we began with, when he cautioned that ‘in this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise.’ In ‘On Toleration,’ Popper reiterated the point, writing that as long as intolerant groups ‘discuss and publish their theories as rational proposals, we should let them do so freely,’ and that, when it comes to people who ‘try to justify the use of violence’ we should simply ‘refute’ their theories (ATOS, 315).

Besides setting a high bar for what counts as ‘intolerance,’ (essentially violence or direct incitement to violence), Popper also stressed that we should resort to coercive suppression of intolerant movements only as last resort. ‘We should claim the right to suppress them if necessary even by force’ (Popper’s emphasis) he says in the endnote on tolerance, ‘for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols.’ This is what takes us to the famous declaration that ‘we should therefore claim, in the name of tolerance, the right not to tolerate the intolerant.’

Reasoned deliberation when possible

In a 1978 letter to the Routledge editor Rosalind Hall, who was requesting permission to re-print some of the paragraph we began with, Popper insisted that he would ‘permit this quotation only if the whole paragraph is quoted, including the words: “Less well known is the paradox of tolerance.”’ The reason, Popper said, was that ‘I want it to be clear that this is proposed by me only incidentally and not as my main statement about tolerance.’

The best candidate for Popper’s ‘main statement’ on tolerance is undoubtedly his 1981 essay ‘On Toleration’; but though we have quoted liberally from it here, the essay soon strays from its purported topic. (A lecture on ‘Toleration and Intellectual Responsibility,’ first given in the same year, covers very similar ground: ISBW, 188-203). It is perhaps not surprising that his single, suggestive note on ‘the paradox of tolerance’ in The Open Society has attracted so much attention, debate, and attempts at co-optation. By surveying a broader range of Popper’s writings, we hope to have shed more light both on that all-important endnote and on Popper’s views about toleration more generally.

Popper thought the limits of tolerance lay where arguments give way to violence (that is, to ‘fists or pistols’). In cases where violence was offered, directly incited, or promised, Popper saw coercion by the liberal democratic state as a justified sort of reciprocity. State coercion, though, was something that should be considered only as a last resort, when violence was obvious or imminent; in all other cases, even when an ideology might strike us as intolerant, we should try to counter it with rational criticism and discussion. 

Reasoned deliberation is, in the final analysis, the antithesis of violence. As Popper put it in the second volume of The Open Society, ‘one does not kill a man when one adopts the attitude of first listening to his arguments’ (OS II, 238). This makes toleration key in the maintenance of modern, pluralistic societies, which will inevitably contain a variety of different beliefs and perspectives, some of them fervently opposed to each other. Toleration follows, besides, from a recognition that we are all fallible: our own chosen beliefs and enthusiasms may, after all, turn out to be wrong, so it would be wrong to try to impose them on others.

Popper would not have countenanced limiting the expression of different viewpoints on the ground of offence or even of ‘harm.’ He would almost certainly have argued strongly against the recent proposals by Jacinda Ardern’s Labour government to outlaw ‘incitement of hatred and discrimination’ against a series of different groups (including groups defined by religious beliefs, ethical beliefs, and political views). 

But Popper’s basic position – that we should tolerate all views and movements that stop short of violence or direct incitement to violence – is not itself a party-political one. The idea that we should not tolerate violence applies equally to any movement that exchanges words for blows. By the same token, Popper’s recommendation that we should tolerate all ideas and life-choices that fall short of violence challenges us to be tolerant of movements across the whole broad spectrum of modern political discourse – if they eschew violence.

In the final analysis, Popper’s proposal that we should tolerate each other up to the point of violence doesn’t constitute an exhaustive account of where we might have to set limits on speech or expression. As the Victoria University legal scholar Eddie Clarke has noted, in a few situations our current laws do enforce some penalties against speech even in the absence of violence (in cases of perjury, say). 

Nevertheless, Popper’s writings on toleration, including his famous ‘paradox of toleration,’ remind us that coercion is as good a place as any to set a hard limit for toleration. Setting the bar as high as coercion leaves citizens space to develop their own ideas and life-paths freely. We should therefore approach any limits to expression below this high bar with some scepticism.  

This emphasis on violence as the line we must not cross puts Popper firmly in the main stream of liberal political thought running through Max Weber (with his emphasis on the state as the possessor of a monopoly on force) as well as John Stuart Mill (who similarly insisted that citizens should be free to develop their ideas uncoerced by others). This tradition of thinking about tolerance is one that has played a large part in the success and development of liberal democracy as a governmental system and a way of life; and it is one that we in today’s New Zealand might take more account of as we continue to debate the nature and limits of toleration. 

ATOS = J. Shearmur and P.N. Turner (eds.), After the Open Society: Selected Social and Political Writings (London: Routledge, 2008)

CR = K.R. Popper, Conjectures and Refutations: The Growth of Scientific Knowledge (London: Routledge, 1963)

ISBW = K.R. Popper, In Search of a Better World: Lectures and Essays from Thirty Years (London: Routledge, 1984) 

OS = K.R. Popper, The Open Society and its Enemies (2 vols., London: Routledge, 1945)

Unpublished material derives almost entirely from the Karl Popper Archive at the University of  Klagenfurt, Austria. It is used with the full permission of the University of Klagenfurt/the Karl Popper Archives. The letter to Eccles comes from the Eccles archive in the Institut für Geschichte, Theorie und Ethik der Medizin, Heinrich-Heine-Universität, Düsseldorf. All rights reserved. 

Header image: The widely-circulated cartoon about Popper’s ‘paradox of tolerance.’ Source: Pictoline.com