Towards the end of last year, the think-tank Policy Exchange recommended the criminalisation of all Jihadist material – not just content that gives direct assistance to the planning and execution of terror. That’s an important category shift: banning bomb construction manuals for wannabe Jihadists or the Dummies guide to terror is obviously desirable.  Suppressing a whole kind of discourse is quite another thing.

The Government is set to unfurl a new raft of anti-terror legislation in coming days that moves us closer to that position. Anyone who genuinely ascribes positive value to free speech should be very worried about this.

The Times reported today that a ‘three strikes’ law would be introduced: ‘The offence of possessing information deemed useful to a terrorist will be widened to include material viewed online three or more times or streamed online. At present it is an offence only if extremist content is downloaded and stored on a suspect’s computer, saved on a separate device or printed.’

The law will be extended to cover ‘reckless’ activity that might encourage support for a banned group.

There is a reasonable and coherent internal logic here – if the state is in the business of criminalising the consumption of Jihadist rhetoric, why should the consumer face charges only at the point of download?  Makes sense doesn’t it – just a harmless attempt to keep legislation up to date with new media, a ‘digital fix’ as Javid puts it.

Free speech is unlucky in its defenders. There are those who only defend free speech when it suits. This administration has made itself vulnerable to that charge – you cannot simultaneously seek to make political capital by attacking the student movement for curtailing free speech and at the same time introduce legislation that could very well have a chilling effect on the free exchange of ideas.

And there are those who defend it on the basis of its absolute value: ‘I disapprove of what you say, but I will defend to the death your right to say it.’ In reality, it’s a nice sounding abstraction.

The human animal is a social animal – we realise life’s value together. Free speech is not an absolute good – it is an imperfect art that aims for an approximate balance between conflicting individual projects and collective goals, and sometimes that means placing restrictions on what can and can’t be said.

Milton, our most eloquent defender of the true value of free speech, was quite aware of that trade-off. Here he is in Areopagatica: ‘the suppressing of scandalous, seditious, and libellous Books’ is welcome, ‘For Books are not absolutely dead things, but doe contain a potencie of life in them to be as active as that soule was whose progeny they are … I know they are as lively, and as vigorously productive, as those fabulous Dragons teeth.’

Books are dragon teeth – Milton encourages us to keep a ‘vigilant eye’ on the evils they can inspire.

However, Milton continues: ‘And yet on the other hand, unlesse warinesse be us’d, as good almost kill a Man as kill a good Book; who kills a Man kills a reasonable creature, Gods Image; but hee who destroyes a good Booke, kills reason it selfe, kills the Image of God.’

We have to be very careful in deciding what constitutes a bad book, because we risk destroying good and important work. The Government is getting that trade-off wrong. It is right and desirable to ban the possession and distribution of material that directly incites violence. It is wrong to ban all Jihadist literature.

Trust me, I’ve read a hell of a lot of it: I wrote a thesis on the Islamic State’s in-house magazine, and I had to read it all. Despite what a dire read it was, it’s important that there are people who know about this sort of material, beyond the narrow intelligence communities, and think about what it means for our own society.

Jihadist culture thrives on mystery, on the promise that it poses a genuine and coherent critique of Western life. That culture needs to be exposed systematically with all the instruments available to us – in broadsheets, in journals, on TV and radio and online, there needs to be a relentless and raucous focus on what Jihadism says, and why it’s wrong.

The Government should immediately give proper assurances to academics and journalists who pursue legitimate research into the phenomenon of radicalisation that they will not be covered by this legislation. If I were beginning my research into the phenomenon again, I would now think twice about it.

That’s what a chilling effect on free speech really means: good books will simply not be written, and he who kills a good book, kills reason itself.