Looking at the letter alone, the evidence seems inconclusive. Juan Cole, who had argued that the salutation was a religious impossibility, has withdrawn that objection and now questions its authenticity on narrower grounds. Expert opinions seem mixed; Michael Scheuer buys it, which gives it some credibility, but then

Ken Katzman, a terrorism expert with the Congressional Research Service -- the in-house think-tank of the U.S. Congress -- said the letter contained elements that raised doubts about its authenticity.

But as billmon demonstrates, the letter cannot be considered in isolation; we have to consider it in the context of Bush's desperate plea for better poll numbers (the same day the letter was released), the New York subway terror hoax (pushed by DHS in the days before Bush's speech), and the supposed terrorist plots we 'disrupted' (which turned out to be less than Bush claimed in his speech).

More to the point, it has to be seen in the context of the Plame investigation, the DeLay indictments, the catastrophic failures in Iraq, and polls that have dropped below 40%.

So the specific question of the letter's authenticity is ultimately secondary. The bigger picture is the exploitation of terror fears in a desperate scramble to change the subject. And the better question is: why would anyone believe anything these people say?