The commission investigating the attacks of Sept. 11, 2001, has a critical dual mission to fulfill -- to help our nation understand how the worst assault on our homeland since Pearl Harbor could have occurred and to outline reforms to prevent new acts of terrorism. ***************SNIP***************** At last week's hearing, Attorney General John Ashcroft, facing criticism, asserted that "the single greatest structural cause for September 11 was the wall that segregated criminal investigators and intelligence agents" and that I built that wall through a March 1995 memo. This is simply not true. First, I did not invent the "wall," which...