These days, I’m constantly impressed by how much of our political debate is affected for the worse by our loss of the language and the very concept of honor — a loss which I have documented in my book Honor, A History (2006). One example comes to mind in the international uproar that has greeted the decision by Mr. Kenneth MacAskill, the Scottish Justice Minister, to release Abdulbaset Ali Mohmed al Megrahi, the only man convicted in connection with the bombing of Pan Am flight 103 in 1988, also known as the "Lockerbie bombing" after the Scottish town where the plane came down with 270 people, including 189 Americans on board. Mr MacAskill’s action was allegedly taken on "compassionate grounds," since Mr Megrahi is suffering from terminal prostate cancer, but the rejoicing in Libya when this mass murderer returned home to a hero’s welcome gives you some idea of what such a disturbingly ill-considered action meant to a robust if primitive honor culture like that which prevails in most of the Arab world. And our bewilderment and outrage at such entirely predictable rejoicing is one measure of our loss of understanding of this central motivation of our enemies.

Compassion is a virtue, but it is a private, a face-to-face virtue which almost invariably ceases to be one when it takes on a public dimension. An act of compassion by a government, in the full glare of publicity, is not a virtue but a bid to be given credit for moral superiority. I leave to one side for the moment the increasingly insistent questions in the British press as to whether, in fact, this act of "compassion" was part of a trade deal with the Libyans. As a public act and therefore in the domain of honor, even if we no longer believe in that honor, it was in any case an admission of weakness, which is naturally how the Libyans and the rest of the Arab world interpreted it. Weakness and fear. We, the compassionate, the proudly moral West have been grievously injured by this terrorist, and yet we decline to make him pay the full price for his crime. In the eyes of those who value honor, and they are many outside the West, that counts as a victory for our enemies in whose name he committed it, and an ignominious defeat for us. To them, we are a beaten animal who shows its throat to an attacker to signify that the fight has gone out of it.

David Blair, writing in the London Daily Telegraph, would even excuse the British government if the release was as a result of that alleged trade deal, claiming that "there is nothing dishonourable about a country deciding where its crucial interest lies and acting accordingly." It’s true, too, that the Libyans’ belief in their own triumph over a craven and cowardly West would be undercut to some extent if it turned out to have been done for Britain’s material advantage, rather than mere compassion. But it’s not a whole lot better for the standing of Western honor in the eyes of the world to be perceived as being capable of any self-abasement in return for a sufficient sum of money. It’s still a loss of honor that could hardly be compensated for by any amount of money and so a much more "crucial interest" than the material. Our failure to understand how honor works allows us the luxury of supposing that the world sees us as we see ourselves: that is, as compassionate and merciful, not weak and cowardly. We may even insist that we are honorable because we arrogate to ourselves the right to decide what the word shall mean. But honor hasn’t gone away because we imagine we have remade it in our own image.

President Obama has expressed his strong disapproval of the Scottish action, which may or may not indicate an understanding of what national honor demands of a statesman. But he gave us another example of the more general failure to understand these demands when he attempted to define the war in Afghanistan as "a War of Necessity" (hooray!) rather than, like the conflict in Iraq, "a War of Choice" (boo!). Writing in yesterday’s Washington Post, Robert Kagan demolished this argument.

The claim of necessity wipes away the moral ambiguities inherent in the exercise of power. And it prevents scrutiny of one’s own motives, which in nations, as in individuals, are rarely pure. This hoped-for escape from moral burdens is, however, an illusion. Just because America declares something necessary doesn’t mean that the rest of the world, and especially its victims, will believe it is just. The claim of necessity will not absolve the United States, and Obama, from responsibility for its actions. As Reinhold Niebuhr pointed out long ago, Americans find it hard to acknowledge this moral ambiguity of power. They are reluctant to face the fact that it is only through the morally ambiguous exercise of their power that any good can be accomplished. Obama is right to be prosecuting the war in Afghanistan, and he should do so even more vigorously. But he will not avoid the moral and practical burdens of fighting this war by claiming he has no choice. An action can be right or just without being necessary. Like great presidents in the past, Barack Obama will have to explain why his choice, while difficult and fraught with complexity, is right and better than the alternatives.

Needless, perhaps, to say — though even Mr Kagan dare not say it — the reason why it is right is that it is honorable. Or, to put it another way, we must either grant or deny our enemies the vindication they sought in destroying the World Trade Center, part of the Pentagon and 3000 American lives in 2001. The unforgiving standard of honor allows no third alternative. And to leave them in possession of the sanctuary they enjoyed in Afghanistan prior to 9/11 would be to grant them that vindication — in effect, to surrender in the great battle of our time. Our post-honor, presumptively pacifist culture supplies us with many opportunities to deceive ourselves that abandoning the fight would really not be surrender but something doubtless very moral and high-minded and disinterested instead. But the silent watchers of the world’s surviving honor cultures will know what it means, even if we don’t. And they will not be inclined to be compassionate.