The National Security Agency is a riddle wrapped in a mystery inside a code. Secrets lie within. Located in Fort Meade, Md., it dwarfs the CIA. Its budget is black, unknown. And, most disturbing of all, it is the world's largest employer of mathematicians.

One of its secrets, recently revealed, is that it's monitoring millions of phone calls to learn just who was calling whom. (Technically, only telephone numbers are being recorded, but you don't have to be Q from James Bond to get a name from a number.) This information was being used to determine who might be a terrorist.

Legal or not, the spying program isn't worth violating our civil liberties for. The information one can glean will hardly help us win the war on terror.

With the NSA data, you can draw a picture with nodes or dots representing individuals, and lines between nodes if one person has called another. Mathematicians who work with pictures like this are called graph theorists. The field of social network analysis deals with trying to determine information about a group from such a graph, such as who the key players are or who the cell leaders might be.

But even when you know everyone in the graph is a terrorist, graphs don't contain information about the order or hierarchy of the cell. Researchers look instead for graph features like centrality: They try to identify nodes that are connected to a lot of other nodes, like spokes around the hub of a bicycle wheel. Monterey Naval Postgraduate School researcher Ted Lewis, in his textbook "Critical Infrastructure Protection," defines a critical node to be such a central hub.

There are two problems. First, the central player might not be as important as the hub metaphor suggests. Jafar Adibi of the University of Southern California looked at e-mail traffic between Enron employees before Enron collapsed, and drew the graph. He found that if you naively analyzed the graph, you could mistakenly conclude that one of the central players was CEO Ken Lay's ... secretary. But that wasn't the person who ran the company into the ground.

Second, as the journal Studies in Conflict and Terrorism reported in 2003, you can kill all the central players in a terrorist cell and still leave the cell with a complete chain of command -- still capable of carrying out a devastating attack.

Expert Kathleen Carley of Carnegie Mellon was able to correctly predict -- twice -- who would take over Hamas when its leaders were assassinated, and her analysis used detailed information about the individuals in the organization, not just what anonymous nodes were linked with what. The moral is that the graph theory approach is inadequate. For useful results, it's important to utilize the lattice theory approach, which takes into account order and hierarchy.

The other questionable aspect of the NSA spying program is that it seeks to work out who might be a terrorist based on their calling patterns. While I agree that anyone calling 1 (800) AL-QAEDA is probably a terrorist, guilt by association is not just bad law, it's bad mathematics, for three reasons.

The simplest reason is that we're all connected. Not in the Haight-Ashbury/Timothy Leary/late-period-Beatles kind of way, but in the sense of the Kevin Bacon game. Sociologist Stanley Milgram took individuals unknown to each other, separated by a continent, and asked one person to send a package to the other -- but only by sending the package to an individual he or she knew, who could then only send the package to someone he knew, and so on. While Milgram's interpretation of the results has since been questioned, the conclusion that emerged is that it took only six mailings, on average, for each package to reach its intended destination.

For example, President Bush is only three steps away from Osama bin Laden. And terrorist hermits like the Unabomber might be connected only to very few people. So much for guilt by association.

The second reason the NSA methodology is flawed is the concept "strength of weak ties," made famous by Stanford sociologist Mark Granovetter. Robert Spulak of the Joint Special Operations University puts it this way: You might not see your college roommate for 10 years, but if he were to call you up and ask to stay in your apartment, you'd let him. This is the principle under which sleeper cells operate: There is no communication for years. The links between nodes that the NSA is looking for simply might not exist for the real threats.

Formal concept analysis, a branch of lattice theory, helps rectify this situation. Individuals who share many of the same characteristics are grouped together as one node, and links between nodes in this picture, called a concept lattice, indicate that all the members of a certain subgroup, with certain attributes, must also have other attributes. For instance, you might group together people based on what cafés, bookstores and mosques they attend, and then find out that all the people who go to a certain cafe also attend the same mosque (but maybe not vice versa). While this tool has in fact been used by researchers at Los Alamos National Laboratory to sift through hundreds of terrorism-related reports, it's still dangerous to rely on the math.

The NSA data mining is flawed because, as Kennedy and Lincoln buffs know, two people can be a lot alike without being the same person. Even if there is only a 1 in 150 million chance that someone might share the profile of a terrorist suspect, it still means that, in a country the size of the United States, two people might share that profile. One is just minding his own business. The other is Cat Stevens.

This isn't to say mathematicians are useless. In September 2004 -- 10 months before the July 7 bombing of the London Underground -- mathematician Gordon Woo warned that London was a hotbed of jihadist radicalism. But Woo, who works for the Bay Area company Risk Management Solutions, didn't anticipate the bombings using math. He used his knowledge and experience of London, especially the Wood Green area. That's what law enforcement officials should be doing.

As for tracking terrorist financing, it may already be too late. The terrorism of the future, according to mathematician Stefan Schmidt of the Technical University in Dresden, Germany, may be the terrorism of the futures -- when bombs explode, the stock market drops. Schmidt wants to quantify the impact on the market of a terrorist incident. The only people who know when a bomb will explode are the terrorists. By playing the market, they may already have obtained as much money as they need -- in perfectly legitimate ways -- thus stifling Treasury Department efforts to cut off the source of their funding.

Math is just a tool. Used wisely, math can indeed help win the Battle of Britain (by breaking the German codes). But used unwisely -- as seems to be the case in the NSA telephone caper -- your approval rating might just hit an all-time low.

Koreans have developed a sense of nation based on shared blood and ancestry. The Korean nation was "racialized" through a belief in a common prehistoric origin, producing an intense sense of collective oneness. Ethnicity is generally regarded as a cultural phenomenon based on a common language and history, and race understood as a collectivity defined by innate and immutable phenotypic and genotypic characteristics.

But historically, Koreans have not differentiated between the two. Instead, race served as a marker that strengthened ethnic identity, which in turn was instrumental in defining the nation. Koreans thus believe that they all belong to a "unitary nation" (danil minjok), one that is ethnically homogeneous and racially distinctive.

Despite 1,000 years of political, linguistic, and geographic continuity - and contrary to popular belief - this sense of ethnic homogeneity took root only in the early 20th century.

Faced with imperialist encroachments, Koreans developed the notion of a unitary nation to show its autonomy and uniqueness. They stressed the ethnic base, rather than civic elements, in defining the Korean nation.

Shin Chae-ho, a leading nationalist, for instance, presented Korean history as one of the "ethnic nation" (minjoksa) and traced it to the mythical figure Dangun. According to him, the Korean people were descendants of Dangun Joseon, who merged with Buyo of Manchuria to form the Goguryeo people. This original blend, Shin contended, remained the ethnic or racial core of the Korean nation, a nation preserved through defense and warfare against outside forces. The nation was defined as "an organic body formed out of the spirit of a people ... descended through a single pure bloodline" that would last even after losing political sovereignty.

The need to assert the distinctiveness and purity of the Korean nation grew even more important under colonial rule, especially as Japan attempted to assimilate Koreans into their empire as "imperial subjects." The Japanese assimilation policy was based on colonial racism, which claimed that Koreans and Japanese were of common origin but the former always subordinate.

The theory was used to justify colonialist policies to replace Korean cultural traditions with Japanese ones in order to supposedly get rid of all distinctions and achieve equality between Koreans and inlanders. Colonial assimilation policy included changing Korean names into Japanese, exclusive use of Japanese language, school instruction in the Japanese ethical system, and Shinto worship.

Koreans resisted by asserting their unique and great national heritage. Yi Kwang-su, a key figure during colonial rule, claimed that "hyeoltong" (bloodline), "seonggyeok" (personality), and "munhwa" (culture) are three fundamental elements of a nation and that "Koreans are without a doubt a unitary nation (danil han minjok) in blood and culture." Such a view was widely accepted among Koreans: To impugn the natural and unique character of the Korean ethnic nation during colonial rule would have been tantamount to betraying Koreanness in the face of the imperial challenge of an alien ethnic nation. Japanese rule did not erase Koreans' national consciousness but rather reinforced their claim to a truly distinct and homogeneous ethnic identity.

After independence in 1945, and despite peninsular division into North and South, the unity of the Korean ethnic nation or race was largely taken for granted. Neither side disputed the ethnic homogeneity of the Korean nation, spanning thousands of years, based on a single bloodline of the great Han race. Instead, both sides contested for the sole representation of the ethnically homogeneous Korean nation. Even today, Koreans maintain a strong sense of ethnic homogeneity based on shared blood and ancestry, and nationalism continues to function as a key resource in Korean politics and foreign relations.

Ethnic national identity has been a crucial source of pride and inspiration for people during the turbulent years of Korea's transition to modernity that involved colonialism, territorial division, war, and authoritarian politics. It has also enhanced collective consciousness and internal solidarity against external threats and has served Korea's modernization project as an effective resource.

At the same time, such a blood-based ethnic national identity became a totalitarian force in politics, culture, and society. It came to override other competing identities and led to the poverty of modern thought, including liberalism, conservatism, and radicalism. It has hindered cultural and social diversity and tolerance in Korean society.

Ethnic nationalism will remain an important organizing principle of Korean society. We cannot ignore ethnic national identity or treat it as a mere myth or fantasy. But neither can we remain simply content with its current role.

Instead, it should be recognized that ethnic nationalism has become a considerable force in Korean society and politics and that it can be dangerous and oppressive when fused with racism and other essentialist ideologies. Koreans must thus strive to find ways to use ethnic nationalism constructively and mitigate its potential harmful effects.

In particular, Koreans must seriously consider the establishment of a democratic

institution that can contain the repressive, essentialist elements of nationalism.

The principle of bloodline or "jus sanguinis" still defines the notion of Korean nationhood and citizenship, which are often inseparable in the mind of Koreans. In its formative years Koreans developed the ethnic base of nation without a corresponding

attention to the political notion of citizenship.

After colonial rule, neither state paid adequate attention or made any serious effort to develop a more inclusive notion of citizenship. Social institutions that can address issues of discrimination against ethnic non-Koreans (for example, ethnic Chinese known as "hwagyo" in Korea) have been largely overlooked. The Korean nationality law is still based on jus sanguinis and legitimizes, consciously or unconsciously, ethnic discrimination against foreign migrant workers.

In this context, most Koreans have stronger attachment to "ethnic Koreans living in foreign countries" than to "ethnic non-Koreans living in Korea." It is also much easier for a Korean-American who supposedly has "Korean blood" to "recover" Korean citizenship than for an Indonesian migrant worker living in Korea to obtain Korean citizenship. This is true even if the Indonesian worker might be more culturally and linguistically Korean than a Korean-American.

Korea needs to institutionalize a legal system that mitigates unfair practices and discrimination against those who do not supposedly share the Korean blood. Koreans need an institutional framework to promote a democratic national identity that would allow for more diversity and tolerance among the populace, rather than simply appeal to an ethnic consciousness that tends to encourage false uniformity and enforce conformity to it.

They should envision a society in which they can live together, not simply as fellow ethnic Koreans but as equal citizens of a democratic polity. It should be an integral part of democratic consolidation processes that Korea is currently undergoing. Otherwise, it would be hard to expect Korea to become "Asia's hub," which will require the accommodation of cultural and ethnic diversity and flexibility.

Discussion of unification is premature and can even be considered dangerous if unification occurs without such change. As the German unification experience shows, a

shared ethnic identity alone will not be able to prevent North Koreans from becoming "second-class citizens" in a unified Korea. Even worse, because of higher expectations resulting from a shared sense of ethnic unity, a gap between identity (ethnic homogeneity) and practice (second-class citizens) will add more confusion and tension to the unification process.

Thus, it will be a major challenge for Koreans to develop democratic institutions that can treat people living in Korea as equal citizens of a democratic polity. This task will be all the more important and urgent as Korea becomes more democratic, globalizes, and also prepares for national unification.

North Korea's response to the United Nations resolution demanding that it suspend its ballistic missile program and resume a moratorium on launches was typically belligerent. But like the multiple launch of seven missiles earlier this month, the North Korean vow to continue to fire off its missiles should not be dismissed as mere political theater.

The missile tests were neither a gesture of defiance nor a desperate bid for negotiations. Nor can they be dismissed as the impulsive act of an irrational leader. It was, as Pyongyang itself so succinctly put it, a "military exercise."

The launches are only the latest evidence of a decadeslong effort by Pyongyang to redress the military balance in its favor. For North Korea, missiles are an attempt to compensate for weakness. The communist state has a large but technologically backward army, lacking the air power to compete with the United States and its South Korean ally. Rockets give it the firepower to back an assault on the South and to hold U.S. forces in Japan, the rear base for Korea, at bay.

The late North Korean leader Kim Il Sung set this goal as far back as 1965 when he established an academy to develop missiles and other modern weaponry.

"If war breaks out, the U.S. and Japan will also be involved," he said. "In order to prevent their involvement, we have to be able to produce rockets which fly as far as Japan."

I encountered one crucial tentacle of Kim's program some 14 years ago, in late October of 1992.

A group of 64 Russian rocket scientists, accompanied by their wives and children, were stopped just as they were about to board a flight to North Korea. The scientists were employees of a super-secret facility in the Urals, the V.P. Makeyev Design Bureau, responsible for the development of the Soviet Union's submarine-launched ballistic missiles.

As the bureau chief for the Christian Science Monitor, I pieced the story together later from Russian press accounts and interviews with the scientists and others. A middleman with apparent official backing had offered the bureau, starving for orders and left adrift by the sudden end of the Cold War, work in North Korea.

Scientists who were making the equivalent of $15 a month jumped at offers of up to $4,000 a month to help a former Soviet ally. In the spring, a group of 10 scientists had gone for an initial foray. The Koreans, one of the scientists told me, initially never directly asked about nuclear warheads or missile designs. They claimed only to be interested in rocket science.

The Russians came home that fall and signed up dozens of their comrades as recruits. But the project was not officially sanctioned, and the KGB held them outside of Moscow for two months while the broker tried to re-negotiate their departure. Russian officials later described the North Koreans' aim, without mentioning them by name, as an attempt to build "combat missile complexes that could carry nuclear weapons."

North Korea began with copies of Soviet short-range Scud missiles and moved on to medium-range "Nodong" missiles, but they lacked the range and accuracy to meet Kim's target. A decade after the airport incident, in 2003, credible reports emerged that the North Koreans were deploying a new, far more accurate missile based on the Soviet SS-N-6, a submarine-launched rocket developed by Makeyev in the 1960s. The Nodong-2, as some labeled it, could reach all U.S. bases in Japan and possibly even to Guam.

In the 1990s, the North Koreans developed a long-range missile, potentially reaching U.S. territory, to lend credence to claims they could deter a pre-emptive strike on their nuclear or missile facilities. Some experts believe the Nodong-2 also functions as the second stage of this missile. American intelligence officials believe an otherwise inexplicable leap in missile technology was thanks to the help of Russian scientists.

Still the self-imposed missile test moratorium that Pyongyang agreed to in 1999 made it difficult to move ahead. Late last year, according to a recent Wall Street Journal story, the North Koreans delivered a dozen Nodong-2 missiles to Iran, a close collaborator on missiles since the 1980s. Unconfirmed reports from Germany say Iran tested the missile in January.

The Nodong-2 may have been tested this month, one of the six short- and medium-range missiles set off in a wave or as a stage of the long-range missile. Data from the launch is not yet conclusive, according to U.S. and South Korean officials. Despite the failure of the long-range attempt, it may be more significant that Pyongyang carried out the first successful launch of a Nodong since 1993 and a nighttime barrage of Scuds and Nodongs.

The display of diplomatic unity at the United Nations may give Pyongyang pause. But the relentless nature of North Korea's pursuit of its ballistic missile strength suggests that this is not a bargaining chip that will be readily traded away.

The European Forum at the Freeman Spogli Institute for International Studies at Stanford University had an eventful and exciting 2005-06 academic year. We organized almost thirty seminars, workshops and other events on cultural, economic and political issues affecting Europe, its relations with the United States and its role in the world.

We hosted several prominent politicians and diplomats during the academic year. In October John Bruton, European Union Ambassador to the United States and former Prime Minister of Ireland (1994-97), presented his views on Europe and the United States as global partners. Earlier during the Fall we were honored to welcome Latvian Foreign Affairs Minister Artis Pabriks. He gave a lecture on Latvia's current challenges in foreign policy and homeland security.

During the Winter term Estonian President Arnold Rüütel visited Stanford. In his talk he addressed such issues as Estonia's relations with the United States, the European Union and Russia. Andras Simonyi, Hungarian Ambassador to the United States, also visited the European Forum. He presented a fascinating lecture on the political and economic situation in Hungary two years into its EU membership. Three more diplomats gave talks during the Winter Quarter. Kurt Volker, Principal Deputy Assistant Secretary of State for European and Eurasian Affairs, spoke about the United States, Europe and the broader Middle East. Dominic Martin, Counsellor at the British Embassy in Washington, talked about the United Kingdom and its current challenges and opportunities in world politics. Richard Morningstar, former United States Ambassador to the European Union, Lecturer at the Stanford Law School and European Forum Research Affiliate, presented his insights into the cooperation between the United States and the European Union in counter-terrorism. This last seminar was part of a series of events the European Forum organized on the manners in which European countries and institutions are dealing with the threat of terrorism, following the attacks in Madrid and London.

The War on Terror was also among the issues addressed by Joschka Fischer, former German Foreign Minister (1998-2005). He visited the Freeman Spogli Institute for International Studies in April and gave a 2006 Frank E. and Arthur W. Payne Distinguished Lecture for a standing room only crowd at the Bechtel Conference Center at Encina Hall. He talked about Europe's prospects in a globalized world and the future of transatlantic relations. British Ambassador Sir David Manning gave an equally well-attended and equally impressive 2006 Frank E. and Arthur W. Payne Distinguished Lecture on energy as a burning issue in foreign policy.

Other events organized on the topic of counter-terrorism included a round-table discussion on anti-terrorism finance, by Jacob Shapiro, Laura Donohue and Khalid Medani, all affiliated to Stanford University, and a lecture on the French experience of counter-terrorism by Jeremy Shapiro from the Brookings Institution. The series of events culminated with a lecture and a seminar by prolific author and columnist Christopher Hitchens. During a visit to the European Forum in May he presented his fascinating and thought-provoking views on the war on terror, and the situation in Iraq and Iran. The series of events on terrorism is to continue during the next academic year and will culminate with a Thinking Terrorism conference in late 2007.

Furthermore, we organized a number of events on other political issues. German sociologist Heinz Bude, from the University of Kassel, presented his views on the most recent German elections from a broad, societal and historical perspective, paying attention to the 1968 student uprisings and their long-term impact on German society. Christian Deubner, from the CEPII research center in Paris, shared his opinions on current developments in French politics, with a focus on the French rejection of the EU Constitution earlier this year and its impact on France's position in the EU. German author Peter Schneider offered his reflections on the cultural differences between Europe and the United States. He compared the relationship between the two continents to a marriage that has its ups and downs, but endures. Josef Joffe, Editor of the German newspaper Die Zeit, pointed at cultural, demographic, political and economic reasons to argue that the European Union is not about to become a new superpower.

Ken Kollman, from the University of Michigan, presented a political-economic model of leadership in federations and applied it to the EU. Bert Martens, an economist at the EU Commission in Brussels, presented an analysis of the EU's export of political and economic institutions to its neighboring countries, and the incentives it provides for regime change. Markus Hadler, a sociologist at the University of Graz and visiting professor at the European Forum during the past academic year, offered an appraisal of democracy in Europe.

Simon Hug, from the University of Zürich, presented a political-economic model of the negotiations for an EU constitution. Yaron Deckel, from the European Broadcasting Service, talked about the most recent Israeli Elections. Cas Mudde, from the University of Antwerp, presented a talk on immigration and the success of populist parties in the Low Countries. Piet Jan Slot, from Leiden University, gave a seminar on the EU's plans for an internal market for services.

We also organized a number of seminars dealing with various aspects of World War II and its aftermath. There was a talk on the effects of the Europeanization of the holocaust on the attitudes toward Jews, by Werner Bergmann from the Technische Universität Berlin. Monica Siegel, from California State University, Sacramento, gave a presentation on memory and reconciliation in France and Germany. Richard Evans, from Cambridge University, talked about coercion and consent in Nazi Germany. Wolfgang Eichwede, from the University of Bremen, gave a seminar on the dissident movement and Samizdat culture in Eastern Europe. Holocaust survivor Leopold Engleitner and his biographer Bernhard Rammerstorfer talked about surviving Buchenwald as a Jehova's Witness. Martina Pottek, from Bonn University, gave a presentation about artistic concepts to commemorate the holocaust.

Andreas Dorschel, Professor at the University of Graz, and Visiting Austrian Chair Professor at the European Forum during the past academic year, presented a lecture on Bruckner and the 19th century fates of origin.

As the next academic year draws near, we anticipate many more prominent speakers to visit the European Forum. Included in our schedule is the Europe Now lecture featuring Daniel Cohn-Bendit in November 2006.

News that AT&T, Verizon and BellSouth gave customer records to the National Security Agency has set off a heated debate over the intricacies of espionage law. But legal or not, this sort of spying program probably isn't worth infringing our civil liberties for -- because it's very unlikely that the type of information one can glean from it will help us win the war on terrorism.

If the program is along the lines described by USA Today -- with the security agency receiving complete lists of who called whom from each of the phone companies -- the object is probably to collect data and draw a chart, with dots or ''nodes'' representing individuals and lines between nodes if one person has called another.

Mathematicians who work with pictures like this are called graph theorists, and there is an entire academic field, social network analysis, that tries to determine information about a group from such a chart, like who the key players are or who the cell leaders might be.

But without additional data, its reach is limited: as any mathematician will admit, even when you know everyone in the graph is a terrorist, it doesn't directly portray information about the order or hierarchy of the cell. Social network researchers look instead for graph features like ''centrality'': they try to identify nodes that are connected to a lot of other nodes, like spokes around the hub of a bicycle wheel.

But this isn't as helpful as you might imagine. First, the ''central player'' -- the person with the most spokes -- might not be as important as the hub metaphor suggests. For example, Jafar Adibi, an information scientist at the University of Southern California, analyzed e-mail traffic among Enron employees before the company collapsed. He found that if you naively analyzed the resulting graph, you could conclude that one of the ''central'' players was Ken Lay's secretary.

And even if you manage to eliminate all the ''central players,'' you may well still leave enough lesser players that the cell retains a complete chain of command capable of carrying out a devastating terrorist attack.

In addition, the National Security Agency's entire spying program seems to be based on a false assumption: that you can work out who might be a terrorist based on calling patterns. While I agree that anyone calling 1-800-ALQAEDA is probably a terrorist, in less obvious situations guilt by association is not just bad law, it's bad mathematics, for two reasons.

The simplest reason is that we're all connected. Not in the Haight-Ashbury/Timothy Leary/late-period Beatles kind of way, but in the sense of the Kevin Bacon game. The sociologist Stanley Milgram made this clear in the 1960's when he took pairs of people unknown to each other, separated by a continent, and asked one of the pair to send a package to the other -- but only by passing the package to a person he knew, who could then send the package only to someone he knew, and so on. On average, it took only six mailings -- the famous six degrees of separation -- for the package to reach its intended destination.

Looked at this way, President Bush is only a few steps away from Osama bin Laden (in the 1970's he ran a company partly financed by the American representative for one of the Qaeda leader's brothers). And terrorist hermits like the Unabomber are connected to only a very few people. So much for finding the guilty by association.

A second problem with the spy agency's apparent methodology lies in the way terrorist groups operate and what scientists call the ''strength of weak ties.'' As the military scientist Robert Spulak has described it to me, you might not see your college roommate for 10 years, but if he were to call you up and ask to stay in your apartment, you'd let him. This is the principle under which sleeper cells operate: there is no communication for years. Thus for the most dangerous threats, the links between nodes that the agency is looking for simply might not exist.

If our intelligence agencies are determined to use mathematics in rooting out terrorists, they may consider a profiling technique called formal concept analysis, a branch of lattice theory. The idea, in a nutshell, is that people who share many of the same characteristics are grouped together as one node, and links between nodes in this picture -- called a ''concept lattice'' -- indicate that all the members of a certain subgroup, with certain attributes, must also have other attributes.

For formal concept analysis to be helpful, you need much more than phone records. For instance, you might group together people based on what cafes, bookstores and mosques they visit, and then find out that all the people who go to a certain cafe also attend the same mosque (but maybe not vice versa).

While researchers at Los Alamos National Laboratory have used this tool to sift through hundreds of terrorism-related reports -- and find connections that human analysts could not have found easily -- it's still dangerous to rely on the math.

This is because, as Kennedy and Lincoln assassination buffs know, two people can be a lot alike without being the same person. Even if there is only a 1 in 150 million chance that someone might share the profile of a terrorist suspect, it still means that, in a country the size of the United States, two people might share that profile. One might be a terrorist, or he might be Cat Stevens.

This isn't to say that mathematicians are useless in fighting terrorism. In September 2004 -- 10 months before the bombing of the London Underground -- Gordon Woo, a mathematician and risk-assessment consultant, gave a speech warning that London was a hotbed of jihadist radicalism. But Dr. Woo didn't anticipate violence just using math; he also used his knowledge of London neighborhoods. That's what law enforcement should have been doing then and should be doing now: using some common sense and knowledge of terrorists, not playing math games.

Math is just a tool. Used wisely, math can indeed help in warfare: consider the Battle of Britain, won in part by breaking the German codes. But use it unwisely -- as seems to be the case here -- and your approval ratings might just hit a new all-time low.