The French philosopher Michel Foucault notes that in all societies discourse is controlled - imperceptibly constrained, perhaps, but constrained nonetheless. We are not free to say exactly what we like. The norms set by institutions, convention and our need to keep within the boundaries of accepted behaviour and thought limit what may be touched upon. The Archbishop of Canterbury experienced the backlash from stepping outside these conventions when he spoke about aspects of Islamic law that might be imported into British life.

Once, a man was held to be mad if he strayed from this discourse - even if his utterings were credited with revealing some hidden truth. Today, he is called "naive", or accused of having gone "native". Recently, the Royal United Services Institute (Rusi) marshalled former senior military and intelligence experts in order to assert such limits to expression by warning us that "deference" to multiculturalism was undermining the fight against Islamic "extremism" and threatening security.

Former US secretary of state Henry Kissinger, in a recent interview with a German magazine, embellished Rusi's complaints of naivety and "flabby thinking". Radical Islam won't stop, he warned, and the "virus" would only become more virulent if the US were to withdraw from Iraq.

The charge of naivety is not limited to failing to understand the concealed and duplicitous nature of Hamas and Hizbullah, Iran and Syria; it extends to not grasping the true nature of the wider "enemy" the west is facing. "I don't like the term 'war on terror' because terror is a method, not a political movement; we are in a war against radical Islam," says Kissinger. But who or what is radical Islam? It is those who are not "moderates", he explains. Certainly, a small minority of Muslims believe that only by "burning the system" can a fresh stab at a just society be made. But Kissinger's definition of "moderate" Islam sounds no more than a projection of the Christian narrative after Westphalia, by which Christianity became a private matter of conscience, rather than an organisational principle for society.

If radical Islam, with which these experts tell us we should be at war, encompasses all those who are not enamoured of secular society, and who espouse a vision of their societies grounded in the values of Islam, then these experts are advocating a war with Islam - because Islam is the vision for their future favoured by many Muslims.

Mainstream Islamists are indeed challenging western secular and materialist values, and many do believe that western thinking is flawed - that the desires and appetites of man have been reified into representing man himself. It is time to re-establish values that go beyond "desires and wants", they argue.

Many Islamists also reject the western narrative of history and its projection of inevitable "progress" towards a secular modernity; they reject the western view of power-relationships within societies and between societies; they reject individualism as the litmus of progress in society; and, above all, they reject the west's assumption that its empirical approach lends unassailability and objective rationality to its thinking - and universality to its social models.

People may, or may not, agree, but the point is that this is a dispute about ideas, about the nature of society, and about equity in an emerging global order. If western discourse cannot step beyond the enemy that it has created, these ideas cannot be heard - or addressed. This is the argument that Jonathan Powell made last week when he argued that Britain should understand the lessons of Northern Ireland: we should talk to Islamist movements, including al-Qaida. It has to be done, because the west needs to break through the fears and constraints of an over-imagined "enemy".

Camouflaged behind a language dwelling exclusively on "their" violence and "their" disdain for rationality, these "realists" propose not a war on terror, nor a war to preserve "our values" - for we are not about to be culturally overwhelmed. No Islamist seriously expects that a "defeated" west would hasten to adopt the spirit of the Islamic revolution.

No, the west's war is a military response to ideas that question western supremacy and power. The nature of this war on "extremism" became evident when five former chiefs of defence staff of Nato states gathered at a think-tank in Washington earlier this year. Their aim was not to query the realism of a war on ideas, but to empower Nato for an "uncertain world".

"We cannot survive ... confronted with people who do not share our values, who unfortunately are in the majority in terms of numbers, and who are extremely hungry for success," Germany's former chief of defence staff warned. Their conclusion was that the security of the west rests on a "restoration of its certainties", and on a new form of deterrence in which enemies will find there is not, and never will be, a place in which they feel safe.

The generals concluded that Nato should adopt an asymmetrical and relentless pursuit of its targets regardless of others' sovereignty; to surprise; to seize the initiative; and to use all means, including the nuclear option, against its enemies.

In Foucault's discourse, he identified a further group of rules serving to control language: none may enter into discourse on a specific subject unless he or she is deemed qualified to do so. Those, like the archbishop, who penetrate this forbidden territory - reserved to security expertise - to ask that we see the west for what it has become in the eyes of others, are liable to be labelled as naively weakening "our certainties" and undermining national resolve.

But do we, who are brushed out of this discourse by the blackmail of presumed expertise, really believe them? Do we really believe, after so much failure, that Islamist alternative ideas will be suppressed by a Nato plunged into an asymmetrical warfare of assassinations and killings? The west's vision for society holds power only so long as people believe it holds power. Do we really think that if force has not succeeded, that only more and greater force can restore belief in the western vision? If that is the limit to western thinking, then it is these "realists", these armchair warriors fighting a delusional war against a majority who "do not share our values", who are truly naive.

· Alastair Crooke is a former security adviser to the EU and founder and director of the Conflicts Forum conflictsforum.org