In a recent essay about the war in Iraq, Victor Davis Hanson noted that the world of Washington was an “echo chamber.” One creditable—or at least listened to—pundit or politician opines in a way the media likes and, presto, a new bit of conventional “wisdom” is born—or at least reinforced. A mere opinion, often ill-informed, frequently at wide variance with the truth, is repeated often enough, and it suddenly acquires the carapace of general currency that, at a distance, can easily be mistaken for fact. As Hanson shows, what has happened with the war in Iraq provides a sterling example of the genre: ...