Since midsummer, the Senate Intelligence Committee has been attempting to solve the biggest mystery of the Iraq war: the disparity between the Bush Administration’s prewar assessment of Iraq’s weapons of mass destruction and what has actually been discovered. The committee is concentrating on the last ten years’ worth of reports by the C.I.A. Preliminary findings, one intelligence official told me, are disquieting. “The intelligence community made all kinds of errors and handled things sloppily,” he said. The problems range from a lack of quality control to different agencies’ reporting contradictory assessments at the same time. One finding, the official went...