After the Charlie Hebdo shootings, heads of state marched abreast in Paris in symbolic defence of France’s long tradition of freedom of speech. This seemed reassuring. But that image was what political consultants call optics – for democracies around the world have recently seen a striking wave of anti-speech legislation.

Amid national mourning over the deaths of the Charlie Hebdo staff – including five cartoonists – four French police officers arrested the cartoonist Zeon for “incitement”, identifying as the cause of arrest anti-Zionist or antisemitic cartoons.

A law in Canada recasts antisemitism so it can include criticism of Israel, and declares that freedom of speech should not be “abused”; supporters cite freedom of speech on campuses as an antisemitic threat that the law should target.

The NDAA: a clear and present danger to American liberty | Naomi Wolf Read more

In Britain the Tories have been fighting for months to introduce a bill to ban “extremists” from UK campuses; a recent iteration casts UK colleges as monitors of “acceptable” speech.

In Australia a new bill mirrors parts of America’s Patriot Act. “Extremist” groups face social media bans in Britain, and the same push is mirrored in democracies around the world. The US National Defence Authorisation Act criminalises speech it sees as offering “material support” to terror groups, without defining what that might be. (Obama’s lawyers confirmed that the journalist Chris Hedges could be arrested under the NDAA for interviewing a terrorist.) Since terror threats are always invoked in these campaigns to justify banning certain kinds of speech, the public in all these countries has been largely passive. Surely, after one terrorist atrocity after another, stamping out the freedom to express “extremist” ideas on college campuses and online is a small price to pay for safety?

But the core assumption on which these politicians, including Cameron, are selling these laws to the public, is simply wrong. The concept underlying such bills is that dangerous ideas are like a virus. You can quarantine them or kill them, like germs. But ideas are like a vast, rushing body of water that will uproot checkpoints and reconfigure a landscape – if barriers are placed in its way. In fact, the history of censorship shows that it is completely useless in stamping out ideas: the fastest way to spread an idea is to censor it.

Censorship by the state (rather than by the church) is a fairly recent invention. Before 1857 it was quite difficult to get arrested for speech in England. The free speech tradition dating back to Milton’s Areopagitica, if not earlier, was so rich that one had to be “disturbing the King’s Peace” for a speech crime to take place, or to be proven (a very high bar) to have committed sedition or blasphemy. Parliamentary debate showed a clear non-partisan bias against censorship bills, and in favour of liberty of expression.

But in 1857 the Obscene Publications Act was passed – followed in 1867-8 by Regina v Hicklin. The Obscene Publications Act criminalised the intent of the author for the first time, asking: did the author intend to inflame improper passions? The Hicklin ruling extended this to criminalising a work’s effect on a reader: if the work could raise a blush on the cheek of a virgin – if the text could “deprave and corrupt” those who might be vulnerable to immorality, then not only had the author committed a crime, but potentially the publisher, distributor and printer had done as well.

The Victorians have become known for their modesty; in fact, we can’t know that, as they were heavily censored by ever escalating speech laws. Oxford’s Ashmolean Museum is currently showing an exhibition of the work of the satirical cartoonist James Gillray; by 1857, a fair amount of his work would have been illegal to print or distribute in Britain.

Speech and writing about male homosexuality and methods of birth control were major targets. From 1857 to 1885 British writers and publishers were subject to an all-out war waged by the state against literature: print runs were confiscated without warrants, costly printing presses were destroyed, and booksellers were arrested and sentenced to months in prison at hard labour. The elderly publisher Henry Vizetelly died after having served hard labour for the crime of selling an insufficiently vague translations of Zola’s Nana. The birth control advocate Annie Besant lost custody of her eight-year-old daughter after being tried for distributing obscene material – that is, staid medical birth-control pamphlets.

The censoring of Ulysses and Lady Chatterley’s Lover turned these serious texts into runaway bestsellers

Irish nationalism – the terrorism of the 19th century – was also targeted by British state censorship; even poems were criminalised as “sedition”. Later the censoring of Ulysses, by James Joyce, Lady Chatterley’s Lover, by DH Lawrence, and Howl, by Allen Ginsberg, turned these serious texts into runaway bestsellers. Did all of this state-led effort to shut people up work? Did legally silencing these voices do away with these ideas? Do we today live in a world without openly gay men or secularism, without birth control, without Joyce, Ginsberg or Lawrence – or the Republic of Ireland? Obviously not. The more censorship was aimed at these ideas, the more the “discourses” about them proliferated, as the critic Michel Foucault might put it.

Speech about communism was censored in 1950s America, and books about communism were burned by the Nazis. Did that kill communism? Did the blacklist and the censor win the day – or was it in fact glasnost, openness and debate that exposed the weaknesses of communist ideology? The “war on communism” confirms that the most effective way to challenge ideas is not to silence them but to engage – to let all sides hear all sides, to hold feared ideas up to scrutiny, and to expose those ideas to free, open dialogue.

History thus confirms that what will best counter “Islamic extremism” – if that is even the role of the state – is open engagement, debate and more and more sunlight. If you look at what actually worked in history, you would not be arresting people for “Muslim extremist” thought or antisemitic cartoons, however unpleasant: you would be holding well-covered, widely translated public debates between moderate Muslim critics of extremism and extremist voices, or between Muslim extremist religious advocates and western rabbis or secularists – and tweeting, Facebooking, televising, and commenting on the debate in real time.

There is one thing censorship laws manage to do effectively: they do help leaders control and intimidate real grassroots dissent and democratic criticism of all kinds by setting in place what US first amendment activists call “a chilling effect”. When states target one group for censorship, they always start with a group that everyone agrees to hate. But soon it is the speech of environmentalists or bank-reform activists, of union leaders or peace activists, that is targeted too. “Terrorism” is used now, as it has been in the past, as the camel’s nose under the tent: to allow the state, as has happened in the US since the Patriot Act, to surveil and regulate everyone’s most personal rights of expression.

Britain pioneered the idea of freedom of speech and expression. It would be heartbreaking if British citizens, the heirs and heiresses of this great tradition, were to be cowed by a manipulative political use of a real enough terror threat into handing over those precious ancient freedoms.