In the wake of the Boston attack, I thought I would share my view of what makes someone a terrorist. Defining terrorism has proven especially daunting. The main reason is that any definition is condemnatory. The word “terrorism” is not a purely descriptive term; it has strong negative connotations. No one says “I’m a proud terrorist.” The definitions offered by writers and legal documents differ, but they converge on two factors: the method of violence chosen by the terrorist, and the fact that his purposes are political. Whatever else he does, the terrorist targets innocent persons in order to further, actually or symbolically, a political cause.

I accept the pejorative connotation of the concept and provide a definition that reflects that condemnation. A terrorist, I stipulate, is someone who (1) outside the traditional war context, (2) uses immoral means (the deliberate killing of civilians), (3) in the pursuit of an unjust political cause. This definition allows us to differentiate categories of violent actors:

1) The War Criminal: Someone who uses violence in the traditional war context and violates ius in bello, for example by deliberately targeting civilians, is a war criminal, but not a terrorist. Example: the Allied bombing of Dresden in World war II.

2) The Unjust Enemy: Someone in the traditional war context who pursues an unjust cause while abiding by ius in bello is an unjust belligerent, but neither a war criminal nor a terrorist. Example: Perhaps the Germans in World War I.

3) The Criminal Unjust Enemy: Someone in the traditional war context who pursues an unjust cause with immoral means. He violates both ius ad bellum and ius in bello. Example: The Germans in World War II.

4) The Freedom Fighter Who is Also a Criminal: Someone outside the traditional war context who pursues a just cause but in violation of ius in bello, for example by targeting civilians, may be considered a freedom fighter who is also a criminal, but not a terrorist. Example: Perhaps the Maqui French Resistance in World War II, or the Roumanian revolutionaries who overthrew Ceaucescu.

5) The Unblemished Freedom Fighter: Someone outside the traditional war context who pursues a just cause using moral means is a fully justified freedom fighter. Example: Hard to find. Maybe the recent Libyan revolutionaries, not sure.

6) The Subversive: Someone outside the war context who pursues an unjust cause with moral means (that is, he does not target innocents) is a  criminal (since he commits insurrection and unjustifiably kills police officers, etc.), but not a terrorist. Example: Perhaps the South Korean sympathizers with the North, should they be willing to take arms against the South Korean government but spare civilians.

7) The Terrorist: Finally, someone outside the war context who pursues an unjust cause using unjust means is a terrorist. Example: the 9/11 attackers.

It follows that if the Boston bombers were justified in retaliating against the American Empire (they had a just cause), they would fall under category (4) above, freedom fighters, but would still be criminals by virtue of the illegitimate means they used (bombing innocents.) If one takes the position (which I favor) that they did not have a just cause, the Boston bombers (like the 9/11 attackers before them) were terrorists, because both their means and their ends were unjust. They were doubly wrong. They were wrong because they targeted civilians. This is enough, of course, to hold them accountable, just cause or not. However, they were also wrong because they pursued an unjustified political objective. This is of course a purely verbal issue, but I think the definition I suggest may help distinguish those categories with more clarity.

There is another reason behind my suggestion that a terrorist should be defined by his advancement of an unjust cause, in addition to his targeting of civilians: A typical terrorist is a principled evildoer. A theory of evil must distinguish between opportunistic evil and principled evil. Most criminals are opportunistic: they act in self-interest. Their goal is to gain something for themselves, wealth, power, or whatever. The ordinary murderer for monetary gain is in this category. But other criminals are principled. They do evil, not out of selfish motives, but because they act out of evil maxims. Terrorists such as Osama Bin Laden and tyrants like Jorge Videla, Adolf Hitler, and the Taliban arguably belong in this category. These persons are typically fanatic and immune to corruption or other temptations. Here, being principled is a vice, not a virtue, because the value of fidelity to one’s principle is entirely parasitic on the validity of the principle. Because the terrorist has an unjust cause, his tenacious efforts to impose divine governance or whatever (to advance his unjust cause) count, morally, against him. The terrorist’s fearlessness (shown by his willingness to die for his cause) and perseverance make him particularly objectionable, fearsome, and difficult to confront. Al Qaeda’s proud admission of their crimes and their firm attachment to the principles in the name of which they commit them make them morally worse than if they acted for personal gain.

Some may think that the fact that they do these things sincerely in the name of Islam makes them less open to criticism. After all, they are principled. I suggest exactly the opposite: we have stronger reasons to fight principled criminals than opportunistic criminals, both because their maxim is evil and because they cannot be easily bribed or persuaded. The only way to stop principled evildoing is, alas, by force.