We must settle on a name for our enemies that doesn't smear all Muslims but does reflect reality

If we are going to defeat our enemies we have to know who they are. We have to know what to call them. We must at least settle on a name – a terminology – with which we can all agree. And the trouble with the fight against Islamic terror is that we are increasingly grappling with language, and with what it is permissible or sensible to say.

When a man sprays bullets at innocent tourists on a beach, or when a man decapitates his boss and sticks his head on the railings, or when a man blows himself up in a mosque in Kuwait – and when all three atrocities are instantly "claimed" by the same disgusting organisation – it is surely obvious that we are dealing with the same specific form of evil. This is terrorism.

But what are the objectives of this terrorism? Is it religious? Is it political? Is it a toxic mixture of the two? And what exactly is its relationship with Islam? Many thoughtful Muslims are now attempting – understandably – to decouple their religion from any association with violence of this kind.

The excellent Rehman Chishti, MP for Gillingham, has launched a campaign to change the way we all talk about "Isil". He points out that the very use of the term "Islamic State" is in itself a capitulation to these sadistic and loathsome murderers. They are not running a state, and their gangster organisation is not Islamic – it is a narcissistic death cult.

Rehman's point is that if you call it Islamic State you are playing their game; you are dignifying their criminal and barbaric behaviour; you are giving them a propaganda boost that they don't deserve, especially in the eyes of some impressionable young Muslims. He wants us all to drop the terms, in favour of more derogatory names such as "Daesh" or "Faesh", and his point deserves a wider hearing.

But then there are others who would go much further, and strip out any reference to the words "Muslim" or "Islam" in the discussion of this kind of terrorism – and here I am afraid I disagree. I can well understand why so many Muslims feel this way. Whatever we may think of the "truth" of any religion, there are billions of people for whom faith is a wonderful thing: a consolation, an inspiration – part of their identity.

There are hundreds of millions of Muslims for whom the word "Islamic" is a term of the highest praise. They resent the constant association of "Islam" with "terrorism", as though the one was always fated to give birth to the other. They dislike even the concept of "Islamic extremism", since it seems to imply a seamless continuum of Muslim belief and behaviour: from liberal to tolerant to conservative to reactionary to terrorist.

Their point is that terrorist violence is alien from Islam, and that is why they argue so strenuously that we should drop all references to "Muslim terrorists" or "Islamic terrorists". They say that any use of the word Islam or Muslim in such a context is actually offensive and derogatory, and helps to alienate the very people we need to win over.

As one Muslim friend put it to me, "you wouldn't talk about Christian terrorists would you?" And there is some truth in that. We don't talk about "Christian terrorism" even in the context of the sectarian violence between Catholics and Protestants in Northern Ireland. Why do we seem to taint a whole religion by association with a violent minority?

Well, I am afraid there are two broad reasons why some such association is inevitable. The first is a simple point of language, and the need to use terms that everyone can readily grasp. It is very difficult to bleach out all reference to Islam or Muslim from discussion of this kind of terror, because we have to pinpoint what we are actually talking about. It turns out that there is virtually no word to describe an Islamically-inspired terrorist that is not in some way prejudicial, at least to Muslim ears.

You can't say "salafist", because there are many law-abiding and peaceful salafists. You can't say jihadi, because jihad – the idea of struggle – is a central concept of Islam, and doesn't necessarily involve violence; indeed, you can be engaged in a jihad against your own moral weakness. The only word that seems to carry general support among Muslim leaders is Kharijite – which means a heretic – and which is not, to put it mildly, a word in general use among the British public.

We can't just call it "terrorism", as some have suggested, because we need to distinguish it from any other type of terrorism – whether animal rights terrorists or Sendero Luminoso Marxists. We need to speak plainly, to call a spade a spade. We can't censor the use of "Muslim" or "Islamic".

That just lets too many people off the hook. If we deny any connection between terrorism and religion, then we are saying there is no problem in any of the mosques; that there is nothing in the religious texts that is capable of being twisted or misunderstood; that there are no religious leaders whipping up hatred of the west, no perverting of religious belief for political ends.

If we purge our vocabulary of any reference to the specifically religious associations of the problem, then we are not only ignoring the claims of the terrorists themselves (which might be reasonable), but the giant fact that there is a struggle going on now for the future of Islam, and how it can adapt to the 21st century. The terrorism we are seeing across the Muslim world is partly a function of that struggle, and of the chronic failure of much Islamic thinking to distinguish between politics and religion.

The struggle is really about power, of course, rather than spirituality – but that does not mean we can ignore the potency of the religious dimension. It doesn't much matter which word we agree on, with Muslim communities, to describe this ideology of terror – Islamism? Islamo-fascism? – but we need to settle on it fast, and then join together to stamp out the phenomenon. If we are going to beat them, we must all at least know their name.