WASHINGTON, D.C. -- Judge Richard A. Posner was in town for a public appearance the other night, and as he is a leading candidate for the title World's Foremost Authority, I thought I would stop by the famous old Willard Hotel to see what he had to say about the 9/11 Commission Report and its legislative by-product, the Intelligence Report Act. Supposedly the legislation improves the capacity of our intelligence community in this time of terror attacks worldwide. Posner, a federal judge and lecturer at the University of Chicago Law School, writes on a broad range of public matters. He writes beautifully on issues that do not invite elegant prose and with a powerful analytical mind. Often he comes to conclusions with which I do not agree. For instance in his book on the impeachment of President Bill Clinton, he reviewed the law and the transgressions of the culprit, concluding that Clinton could be impeached but should not to be. Well, Judge, I was with you part of the way.

 Now he was in Washington to discuss his most recent book, "Preventing Surprise Attacks: Intelligence Reform in the Wake of 9/11," which is part of a promising series of brief books that the Hoover Institution is publishing on pressing political, economic and social issues. As usual Posner's approach reminds me of another brilliant, if unconventional, policy scholar -- the late Edward Banfield. Banfield, a Harvard government professor of two decades back, employed vast learning and a skeptical intelligence to arrive at conclusions that ended up being commonsensical, and thus, to his fellow scholars, deeply disturbing.

 On the 9/11 Commission's findings and the consequent legislation, Posner's most optimistic judgment is that the legislation is hazy. It leaves the president and intelligence reformers much room in which to revise the commission's recommendations, and they had better use all the room available because they will need it to improve intelligence. His additional judgment is very much like one Banfield might render, to wit, there is no "solution" to the intelligence problem. Surprise attacks are by their nature surprising. While we attempt to thwart the next 9/11, the terrorists are working on something new. Will the intelligence community anticipate it and prevent it? That is hard to say, though we had better try.

  "The commission's report," Posner writes, "mentions only in passing the greater potential threat posed by weapons of mass destruction in the hands of terrorists or enemy states. Deadly pathogens, lethal gases, and even small atomic bombs can be fabricated almost anywhere in the world and, because of their small size, delivered surreptitiously to the United States and activated by a small number of terrorists or foreign agents." Posner goes on: "An active program of foreign intelligence of unprecedented scope and technological sophistication is needed -- and more: a program that can anticipate technological surprises in the form of new, more lethal weapons of mass destruction or means of delivering them."

 As for the reforms in place, Posner is skeptical of their usefulness. Yet there is one reform that he seems to favor, though it is not now in place. The domestic intelligence function now in the hands of the FBI should be "carved out" and placed in a different authority. That new authority would operate as does the United Kingdom's Security Service (MI5). Unlike the FBI today, MI5 is not a police force vested with pursuing terrorists with the intent of prosecuting them. The prosecution of them is a distraction best left to a police force, namely the FBI. Such a reform, Posner agrees, creates civil liberties problems. Yet he believes the problems can be overcome for the good of prosecuting criminals and of gathering still more information on domestic terror plots. It has worked well in the UK and might work well here.

 Posner makes the interesting point that the 9/11 Commission did not study intelligence gathering by other, possibly more seasoned, intelligence agencies in countries such as the UK and Israel. Nor did the 9/11 Commission avail itself sufficiently to the expertise of Americans with superior knowledge and experience in intelligence. He mentions the loss that the commission suffered when Henry Kissinger was barred as chairman, apparently for political reasons. His book is among the finest analyses of intelligence gathering and of intelligence reform I know of. It rests on an insight into intelligence that the historian Paul Johnson made years ago. Johnson's insight is useful to those who underestimate the difficulty of the topic.

 Says Johnson: "Intelligence reports are like reading spy novels with the last chapter missing, because you never know what actually has happened in the end." To be sure, Posner is aware of the murkiness of intelligence. Readers of this book will become aware of the huge job ahead in the struggle against terrorists.