My 9/11 blog post Five Years After was re-posted on LRC this weekend. The new version is substantially identical to the old one, except that it includes this additional paragraph:
The fifth anniversary was marked by commemorations amounting to an apotheosis of the American State, with endless images of waving flags, and endless posturing. The 9/11 attacks were repeatedly referred to as “the worst terrorist attack in history” (conveniently forgetting Hiroshima, Nagasaki, Dresden …). The president spoke earnestly about children who “still long for the daddies who will never cradle them in their arms” (as though having one’s father killed was something only suffered, never caused, by Americans) and about “fighting to maintain the way of life enjoyed by free nations” (as though ending lives abroad and destroying freedom here were the natural way to do this). “America did not ask for this war,” he proclaimed innocently, as though the terrorists’ actions were something other than a response to, and in large part a mirror image of, U.S. foreign policy in the years prior to 9/11.
I’ve received surprisingly little hate mail over this LRC post; but many readers have written (I’ve been away from email all weekend and so am just seeing their responses now) to ask me why I seem to accept the official governmental version of what happened, i.e., why I make no reference to the various 9/11 conspiracy theories. 
The simple answer is that while I’ve read and watched a number of presentations defending such theories, I’m simply not technically competent to evaluate them. When two purported scientific experts disagree as to whether, for example, a jet fuel fire could be hot enough to melt steel in the manner that is supposed to have occurred, I don’t see that I, who know nothing about jet fuel fires or the melting point of steel, am in any position to decide between them. (Nor, I suspect, are most of the people on either side of the controversy.)
I accept the official story provisionally, as supported by the preponderance of the evidence I understand, but with no especial conviction. I’ve studied a few conspiracy theories closely enough to form a cautious opinion – for example, I think the official story on the Holocaust is pretty much correct, and that the official story on the JFK assassination is very likely wrong (though I have no one particular alternative theory I’m plumping for on that one) – but I don’t have the time or inclination to investigate every conspiracy theory closely enough to make an informed judgment, particularly if doing so involves mastering details of chemistry and structural engineering.
A word about conspiracy theories: I think there are two kinds of mistakes to make in regard to them.
One kind of mistake is to be overly dismissive of such theories. One often hears people say “oh, I don’t believe in conspiracy theories” – any conspiracy theories, apparently, as though “conspiracy” were a term without referents. But that’s pretty silly, for everybody is committed to recognising some conspiracy theories as true. For example, as conspiracy theorists rightly like to point out, the official story on 9/11 is as much a conspiracy theory as the dissident version; ditto for the Holocaust. The Manhattan Project, too, was a government conspiracy involving massive numbers of people, and yet kept successfully secret from the public in precisely the way that critics of conspiracy theories like to claim is impossible.
The opposite kind of mistake is to be too receptive to conspiracy theories. The core of this mistake is the assumption that the only alternative to conspiracy is coincidence – as when conspiracy theorists refer to their opponents as “coincidence theorists.” Thus when the number of suspicious correlations becomes too high to be plausibly labeled a coincidence, the conspiracy theorist infers deliberate coordination. But given the central role of invisible-hand explanations (both beneficent and maleficent ones – spontaneous order and spontaneous ordure) in social science, any approach to the explanation of historical events that limits itself to coincidence and conspiracy is pretty hard up for categories.
As I’ve written elsewhere:
Conspiracy theories should not necessarily be regarded as inherently suspect. After all, the greater the extent to which power is concentrated in a society, the easier it is to form an effective conspiracy (because the number of people that need to be involved to pull off a major change is smaller); so we should predict that more conspiracies will indeed occur in societies with centralized power. However, it is also true that incentive structures can coordinate human activities in ways that involve no conscious cooperation.
(“Toward a Libertarian Theory of Class,” pp. 331-2n.; in Social Philosophy & Policy 15. no. 2 (Summer 1998), pp. 303-349.)
In any case, as Brad Spangler recently pointed out, even if the official story on 9/11 is true – that is, even on the interpretation most favourable to those in power – the government is still largely to blame for the attacks. Even accepting its own official version, the government helped to provoke those attacks, was powerless to prevent them, and continues to provoke further attacks it would also be powerless to prevent – all the while using the whole cycle as a pretext for foreign wars and domestic oppression. The defendant may have committed crimes to which he hasn’t confessed; but those to which he has confessed are enough to hang him.