The Paradox of Tolerance

In 1945, as Europe emerged from the devastation of National Socialism, Karl Popper identified a vulnerability within liberal civilization. A society committed to toleration could permit an intolerant movement to exploit its freedoms, acquire power, and destroy the freedoms that had enabled its rise. Popper called this the paradox of tolerance.¹

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.

The decisive distinction is between an intolerant opinion and a movement determined to impose that opinion through coercion. Popper did not prescribe censorship whenever views were offensive, irrational, or objectionable. He expressly preferred rational argument and public opinion wherever those methods could prevail. His warning concerned movements that reject reciprocal argument and teach their followers to substitute force for persuasion.

Three behaviors of the intolerant

Popper did not announce a formal three-part test. His account nevertheless identifies a sequence of recognizable behaviors: denouncing reasoned argument as illegitimate; insulating followers from competing arguments by portraying them as deception; and answering opponents with intimidation or violence. These behaviors can reinforce one another until the open society loses the capacity to defend itself.

For Popper, tolerance was not indifference to the destruction of tolerance. Political rights are sustainable only where institutions and citizens remain willing to protect the conditions of peaceful disagreement. A movement that attacks those conditions presents a different problem from a peaceful critic of prevailing values.

After the Cold War: complacency and its critics

During the decades after 1945, the Cold War dominated Western strategic attention. Nuclear rivalry and the struggle between Soviet communism and liberal democracy overshadowed many other ideological conflicts. The Soviet Union formally dissolved in December 1991. In the atmosphere that followed, Francis Fukuyama argued that liberal democracy might represent the endpoint of humanity’s ideological evolution: no rival model of government appeared to offer a more universally persuasive claim to legitimacy.²

Fukuyama also saw a danger within liberal democracy’s apparent success. Borrowing Nietzsche’s image of the “last man,” he asked whether a prosperous, secure citizenry might lose its appetite for excellence, sacrifice, or struggles undertaken for something greater than comfort. This figure may prefer accommodation even when accommodation becomes a form of surrender. The connection to Popper is an interpretation rather than an argument Fukuyama himself made: a society whose citizens no longer wish to defend its liberties may find that those liberties are remarkably easy to lose.³

The challenge of militant jihadism

The attacks of September 11, 2001 exposed a form of ideological violence for which tolerance was not a reciprocal civic principle. Al-Qaeda’s attack on civilians, the later atrocities of the Islamic State, and the Taliban’s coercive political order provide clear modern applications of Popper’s warning. In these movements, dissent is not simply judged wrong: it can become an offense to be punished. Independent voices are silenced, individual liberties subordinated to ideological authority, and violence represented as a religious or political duty.

The October 7, 2023 Hamas-led assault on Israel, including the killing and abduction of civilians, provides another example of deliberate violence used in pursuit of ideological and political objectives. These organizations have different histories, doctrines, constituencies, and strategic goals. The common feature relevant to Popper is their demonstrated willingness to employ coercion against those they regard as enemies or dissenters, rather than to accept a political order based on reciprocal liberties.

The ideological roots deserve direct discussion. Islam historically developed as a religious tradition with substantial legal and political dimensions. The Arabic dīn (دِين) carries meanings that include religion, obligation, and judgment; its meaning cannot be reduced to the modern Western notion of private belief. Qur’anic passages 9:33, 48:28, and 61:9 proclaim the eventual ascendancy of the true dīn; 8:39 connects fighting with the ending of fitna and the establishment of religion for God. Their interpretation has been debated, but classical Islamic legal scholarship unquestionably elaborated theories of political rule, jihad, and the jurisdiction of Islamic law.⁴

The juristic distinctions between dār al-Islām and territories beyond Islamic rule, and al-Mawardi’s systematic account of government in al-Aḥkām al-Sulṭāniyya, demonstrate that political sovereignty is not an incidental subject invented by modern extremists. Radical jihadist movements selectively invoke this inheritance, often in ways vigorously disputed by other Muslims. The historical existence of an Islamic political tradition and the conduct of particular militant movements are related questions, but they are not identical.⁵

This history makes the political claims of extreme jihadism intelligible. It does not require the fiction that Islam has only a private devotional dimension, nor the equally unsound inference that every religiously observant Muslim endorses a jihadist political project. Popper’s test concerns what movements do with their claims to truth and authority. An organization that suppresses dissent, prevents free inquiry, and enforces doctrine by violence displays precisely the danger he described.

The internet as a force multiplier

The internet has accelerated the circulation of propaganda, reduced barriers to recruitment, and enabled dispersed sympathizers to find one another. A terrorist movement no longer needs to control an extensive print apparatus or a local meeting hall to reach an international audience. These changes amplify the dangers Popper identified without changing their underlying character.⁶

First, ideologically enclosed communities can denounce criticism not by answering it but by labeling every outside source corrupt, blasphemous, or malicious. Second, digital networks can reward conformity and punish dissent through ostracism, intimidation, and organized harassment. Third, threats, doxxing, fabricated images, and coordinated campaigns can silence speakers who would otherwise participate in public debate. When these practices lead to credible threats or violence, the parallels with Popper’s “fists or pistols” become unmistakable.

Algorithms can compound these effects, but claims about their influence require care. Research finds that moral-emotional language can spread more readily in political networks and that false news has sometimes circulated farther and faster than true news. These findings do not demonstrate that social-media algorithms invariably close minds or that every disagreeable online campaign is the equivalent of physical force.⁷

The distinction is important because a new apparatus for policing opinions can become another threat to freedom. Government censorship and opaque corporate control over public discussion may themselves suppress the rational contest of ideas on which Popper relied. The right response is to defend lawful expression, investigate genuine threats, and confront coercive organizations within accountable legal institutions. Policing violence and intimidation is a different undertaking from appointing officials to determine which political opinions are acceptable.⁸

Conclusion: tolerance requires a defense

Popper’s warning has lost none of its force. A tolerant civilization cannot survive by allowing coercive movements to use its freedoms as instruments for abolishing those freedoms. Extreme jihadism supplies an unmistakable example: where its militants gain power, they have repeatedly displaced argument with commands, independent judgment with enforced orthodoxy, and dissent with punishment.

The remedy is neither blanket suspicion of religious believers nor an indiscriminate campaign against unpopular speech. It is a clear-eyed determination to preserve the institutional conditions of freedom: equal protection under law, the right to dissent, freedom of conscience, and the capacity to resist organized intimidation and violence. Tolerance survives when it has the courage to defend itself.