WASHINGTON -- Almost 2 inches thick and 850 pages long, the congressional inquiry into the Sept. 11 attacks largely boils down to two intriguing words: What if? What if an FBI agent had known that two acquaintances of his San Diego informant had been identified as terrorists and would turn out to be among the hijackers? What if agencies had shared more information? What if intelligence agencies had more spies in Afghanistan? What if fighting Osama bin Laden had been a higher priority?