Even before September 11, hardly anyone was advocating terrorism--not even those who regularly practice and support it. The practice is indefensible now that it has been recognized, like rape or murder, as an attack upon the innocent. The victims of a terrorist attack are ordinary men and women, eternal bystanders. There is no special reason for targeting them. The attack is launched indiscriminately against the entire class. Terrorists are like killers on a rampage, except that their rampage is purposeful and programmatic. It aims at a general vulnerability. Kill these people in order to terrify those. A relatively small number of dead victims makes for a very large number of living and frightened hostages.

This is the ramifying evil of terrorism: not just the killing of innocent people but also the intrusion of fear into everyday life, the violation of private purposes, the insecurity of public spaces, the endless coerciveness of precaution. A crime wave might produce similar effects, but no one plans a crime wave; it is the work of a thousand decision makers, each one independent of the others, brought together only by the invisible hand. Terrorism is the work of visible hands--an organizational project, a strategic choice, a conspiracy to murder and intimidate. No wonder the conspirators have difficulty justifying in public the strategy that they have chosen.

But when moral justification is ruled out, the way is opened for ideological apology. In parts of the European and American left, there has long existed a political culture of excuses focused defensively on one or another of the older terrorist organizations: the IRA, FLN, PLO, and so on. The arguments are familiar enough, and their repetition in the days since September 11 is no surprise. Still, it is important to look at them closely and reject them explicitly.

The first excuse is that terror is a last resort. The image is of oppressed and embittered people who have run out of options. They have tried every legitimate form of political action, exhausted every possibility, failed everywhere, until no alternative remains but the evil of terrorism. They must be terrorists or do nothing at all. The easy response is that, given this description, they should do nothing at all. But that doesn't engage the excuse.

It is not so easy to reach the last resort. To get there, one must indeed try everything (which is a lot of things)--and not just once, as if a political party or movement might organize a single demonstration, fail to win immediate victory, and claim that it is now justified in moving on to murder. Politics is an art of repetition. Activists learn by doing the same thing over and over again. It is by no means clear when they run out of options. The same argument applies to state officials who claim that they have tried everything and are now compelled to kill hostages or bomb peasant villages. What exactly did they try when they were trying everything?

Could anyone come up with a plausible list? "Last resort" has only a notional finality. The resort to terror is not last in an actual series of actions; it is last only for the sake of the excuse. Actually, most terrorists recommend terror as a first resort; they are for it from the beginning.

The second excuse is that they are weak and can't do anything else. But two different kinds of weakness are commonly confused here: the weakness of the terrorist organization vis-à-vis its enemy and its weakness vis-à-vis its own people. It is the second type--the inability of the organization to mobilize its own people--that makes terrorism the option and effectively rules out all the others: political action, nonviolent resistance, general strikes, mass demonstrations. The terrorists are weak not because they represent the weak but precisely because they don't--because they have been unable to draw the weak into a sustained oppositional politics. They act without the organized political support of their own people. They may express the anger and resentment of some of those people, even a lot of them. But they have not been authorized to do that, and they have made no attempt to win any such authorization. They act tyrannically and, if they win, will rule in the same way.

The third excuse holds that terrorism is neither the last resort nor the only possible resort, but the universal resort. Everybody does it; that's what politics (or state politics) really is; it's the only thing that works. This argument has the same logic as the maxim "All's fair in love and war." Love is always fraudulent, war is always murderous, and politics always requires terror. In fact, the world the terrorists create has its entrances and exits; we don't always live there. If we want to understand the choice of terror, we have to imagine what must often occur (although we have no satisfactory record of this): A group of men and women, officials or activists, sits around a table and argues about whether or not to adopt a terrorist strategy. Later on, the litany of excuses obscures the argument. But at the time, around the table, it would have been of no use for defenders of terrorism to say, "Everybody does it," because they were face-to-face with people proposing to do something else. Terrorism commonly has its origins in arguments of this sort. Its first victims are the terrorists' former colleagues, the ones who said no to terrorism. What reason can we have for equating these two groups?

The fourth excuse plays on the notion of innocence. Of course, it is wrong to kill the innocent, but these victims aren't entirely innocent. They are the beneficiaries of oppression; they enjoy its tainted fruits. And so, while their murder isn't justifiable, it is ... understandable. What else could they expect? Well, the children among them, and even the adults, have every right to expect a long life like anyone else who isn't actively engaged in war or enslavement or ethnic cleansing or brutal political repression. This is called noncombatant immunity, the crucial principle not only of war but of any decent politics. Those who give it up for a moment of schadenfreude are not simply making excuses for terrorism; they have joined the ranks of terror's supporters.

The last excuse is the claim that all the obvious and conventionally endorsed responses to terror are somehow worse than terrorism itself. Any coercive political or military action is denounced as revenge, the end of civil liberty, the beginning of fascism. The only morally permitted response is to reconsider the policies that the terrorists claim to be attacking. Here, terrorism is viewed from the side of the victims as a kind of moral prompting: Oh, we should have thought of that!

I have heard all these excuses in the past few days--often expressed along with great indignation at the chorus of national unity and determination. But the last two have been the most common. We bomb Iraq, we support the Israelis, and we are the allies of repressive Arab regimes like Saudi Arabia and Egypt. What else can we expect? Leave aside the exaggerated and distorted descriptions of American wickedness that underpin these excuses. There is a lot to criticize in our country's foreign policy over the past decades. Many of us on the American liberal-left have spent the bulk of our political lives opposing the use of violence by the U.S. government (though I and most of my friends supported the Gulf War, which ranks high in the standard version of the fourth excuse). As Americans, we have our own brutalities to answer for--as well as the brutalities of other states that we have armed and funded. None of this, however, excuses terrorism; none of it even makes terrorism morally understandable. Maybe psychologists have something to say on behalf of understanding. But the only political response to ideological fanatics and suicidal holy warriors is implacable opposition.