Can we safeguard the critical secrets needed to protect national security while we enhance the essential scientific openness required for global leadership? It's a tough question, and it's an old one. But the issue is now urgent once again. Calls for curtailing international research exchanges were ignited by the news that sensitive nuclear weapons information at the Los Alamos National Laboratory may have been leaked to the Chinese. As a result, broad-scale investigations and rifle-shot scapegoating have riveted Washington. But the recent months of incendiary congressional hearings and quick reorganizations of the U.S. Department of Energy - no matter how patriotic and well-intentioned - have not resolved the underlying choices about a long-range security strategy.

We need to step back and assess the rationale for scientific cooperation between researchers in the United States and those abroad. A central principle is that strongly enforced safeguards must be in place to protect the most sensitive information, with zero tolerance for lax security and espionage. But overzealous and bureaucratic security measures would shut down thousands of productive scientific exchanges every year. That must not be tolerated either. The costs of such a system to the advancement of science would be higher than the benefits.

National vitality in research is at risk whenever security-obsessed systems erode the freedom to engage in global scientific cooperation. If we overreact to charges of espionage, then the United States would be practicing an ideological reflex that has always been the enemy of scientific and technological progress. Open exchanges accelerate research that not only enriches our lives but also bolsters our nation's security. That was true in the past and is equally true today. With many countries expanding their base of science and engineering, the United States must participate in the global marketplace of ideas.

A recent report by the committee of the National Research Council evaluated the tensions inherent in conducting some secret weapons-related research without compromising the spirit of scientific openness. The report points out that approximately 75 percent of the work being done at U.S. weapons laboratories is unclassified and depends on contributions of scientific research performed in other countries. For example, research aimed at harnessing nuclear fusion as a commercially viable energy source is of great importance to many nations because such energy could potentially offer a virtually inexhaustible fuel supply. But the research budgets of Japan and several European nations in this area far exceed that of the United States. This country must remain involved in international collaboration to be meaningfully engaged in nuclear fusion research.

International cooperation in scientific research also strengthens national security. Consider the cooperative program that has U.S. and Russian scientists working together to upgrade the protection and control of weapons-grade nuclear material in Russia. The program directly serves U.S. security interests by reducing the risk that the material could become available to a rogue nation or terrorist group. Moreover, cooperation with scientists in other countries is essential to implement and verify nuclear arms reductions agreements.

If the United States is to remain the world's largest technological leader, it must remain deeply engaged in the international enterprise of science. U.S. laboratories must be able to attract the best and brightest scientists and engineers from other countries to meet the demands of an ever-changing world. This is the reality for modern research. Just look at the contributions of foreign-born individuals to national security during the past half-century - including many giants of science such as Albert Einstein, Enrico Fermi, Eugene Wigner, Leo Szilard, Edward Teller, Hans Bethe, John Von Neumann, and Stanislas Ulman.

Our country has long been committed to the value of international cooperation in science. The tradition began with Thomas Jefferson, who observed, "the brotherly spirit of Science . . . unites into one family all its votaries of whatever grade, and however widely dispersed through the different quarters of the globe." Even during the Cold War, the dangers of excessive secrecy were highlighted by the Department of Defense in a report, which noted that "classification of technical information impedes its flow within our own system, and may easily do far more harm than good by stifling critical discussion and review or by engendering frustration." The United States must sustain the long and fruitful tradition of scientific openness.