"Why is freedom of expression deemed more important than Jewish lives?" asked Melanie Phillips in The Times this week. Her argument was that Western commentators were failing to report the virulent antisemitism at the heart of the Islamist terrorists' campaign of violence.

Well, I'm committed to the defence of Jewish lives and of freedom of expression. I can't conceive of security for the Jews without a flourishing of Enlightenment values of liberal political rights, religious liberty and free expression. They are indivisible.

That needs to be stressed against a popular and stubborn misconception. This is the view that free speech, while valuable, needs to be balanced against other social goals, such as the maintenance of social cohesion and the avoidance of offence.

On the very day that a dozen French journalists were murdered, one commentator for the Financial Times observed that "too often editorial foolishness has prevailed at Charlie Hebdo". The insinuation that by exercising free speech irresponsibly, the cartoonists and their colleagues had provoked their own murders, was worse than indecent: it was wrong.

There is literally nothing that Western societies can do that will not be taken as a provocation by theocratic extremists. The right response is to defend not only the right of free speech in abstract terms but to accept that it will cause mental anguish and offence - and that there is nothing wrong in this.

Free speech should not be balanced against other social goals

We have been here before, when in 1989 Ayatollah Khomeini of Iran issued an edict suborning the murder of Salman Rushdie for the crime of writing a novel. The then Chief Rabbi, Dr Immanuel Jakobovits, lamentably remarked: "Both Mr Rushdie and the Ayatollah have abused freedom of speech."

Mr Rushdie had done no such thing. He had satirised the religious beliefs of Muslims. Charlie Hebdo did likewise. That's what free speech entails. It is how knowledge advances.

The notion that people's deeply held convictions, merely by being deeply held, merit respect is inimical to the principles of a free society. Beliefs merit respect to the extent, and only to the extent, that they can withstand scrutiny, evidence and criticism - even mockery and derision.

The notion that avoiding (let alone punishing) offence is any part of public policy is pernicious. If the state starts concerning itself not just with citizens' welfare but with their feelings, there is no limit to how far it can encroach on liberty. We shouldn't go there.

Does this mean that we should defend the rights even of racists, demagogues and Holocaust deniers to freedom of expression? Yes, I believe it does, and I have defended in print the civil liberties of such noisome personalities as David Irving, Nick Griffin and Geert Wilders.

The proper objection to Holocaust denial is not that it's offensive (though it certainly is) but that it's utterly false.

Once we accept that people have a right to be protected from hearing fraudulent and inflammatory nonsense, we concede that the truth is an inadequate defence.