In case you have not noticed, we are at war! And it is a global, cosmic, open-ended, potentially eternal war. This war is on terror, but what are we doing about it?

Before you and I can do anything, we ought to know what terror is. Alas, there is no agreed definition. We are at war against a miasma. So long as terror is undefined, our leaders can claim indiscriminate authority and we have no way of determining whether their tactics or targets are well chosen. And there are two other problems. First, we have no real way of telling if the war is going well; and second, we lack the means to judge when, if or how this war will come to an end.

Terror is all about fear and coercion. In which case, the war against terror, with the permanent, pervasive war psychosis it has caused, is itself a form of terrorism. It instils unending fear of the threat. This fear coerces whole societies to curtail liberties defended for centuries as the true bastions of their freedom and security. This is what you get for lack of a sensible definition.

But surely we all know terrorism when we see it? It leaves the blood of innocent bystanders on the floor and, as I have witnessed myself, spatters bits of what were once human beings on walls and ceilings. But my point is, any use of violence leads to such carnage. Indeed, when it comes to violence, our dark instincts have never been short of ways to inflict pain and suffering that are cruel and unusual. To demean, humiliate and strip people of their common humanity is a form of violence. We have an agreed definition of this violence: we call it torture.

The recognition of torture as illegal is part of international law. This definition of principles beyond national law is a proof of our commitment to bettering humanity's lot, a demonstration that we have matured as moral beings. The betterment exists more in the breach than the observance. But the struggle to define what is acceptable, to distinguish clearly what should and should not be permitted, at least means we know when we fail.

So why do we have no definition of terrorism? Why do we lack clear criteria to distinguish what is right from what is wrong in the "war on terror"? Why no agreed regulation for waging a campaign to eradicate terrorism? I think this is because we have a truncated view of terrorism. We can see the terrorism of others only, not the terrorism we visit on others. And we see it only in a physical dimension, not also in political, cultural, economic and ecological terms. In other words, we don't see terrorism in its total context.

As a tactic, terrorism can be wielded as much by states and nations as by non-state groups. As coercive intimidation, terrorism can be used to promote, defend or sustain a view of the world to which all should submit. In which case what is the difference between colonialism, neoconservatism and jihadist extremism? Terrorism has been used to promote both just and unjust causes. So there is more to terrorism than the glib aphorism "One man's terrorist is another man's freedom fighter". The question is: what is that "more"?

I will be chairing a series of seven public lectures at City University, London, starting on 25 April, that will explore this very question. The first talk, "Where Do Terrorists Come From?", is based on the assumption that before we can confront terrorism we have to define it. It is the only way to determine whom or what to oppose, and how to defeat the threat posed to the peace and security that all people, here and in the Muslim world, crave and should be entitled to enjoy.