Nearly 400 years ago, Francis Bacon heralded the dawn of a new era of science and technology, when knowledge and power would be joined in one goal and scientists, rather than priests, would provide authoritative guidance for humanity. Henceforth, according to Bacon, scientists would secure and augment their prestige in society not so much by their dazzling theoretical insights as by the mastery of nature that their practicable science would confer on other men. Bacon predicted that the fruits of the new science would include not only inventions for the relief of human misery but also weapons of immense destructive power.

The Baconian project seemed to reach its zenith in the mid-20th century, when a small group of brilliant theoretical physicists unlocked the secrets of nuclear energy and collaborated on the invention of the nuclear reactor and the atom and hydrogen bombs. Edward Teller, now 94 years old, is among the last survivors of that titanic generation of physicists who permanently altered our world through their work on the Manhattan Project. Teller, who was involved in the race to build the atom bomb from its inception, is now famous-or more often notorious-as "the father of the hydrogen bomb." But Teller was also an early member of that select band of European theoretical physicists who, in the decades between the two world wars, laid the foundations of quantum mechanics, the comprehensive theory of matter and energy on which our understanding of nature now rests.

Teller's memoirs, written with the aid of Judith Shoolery, are a fascinating record of the mutual entanglement of theoretical physics and world politics in the 20th century. Perhaps never again will a handful of theoretical scientists wield the enormous influence on world history that Teller and his colleagues exercised in the final months of World War II. Besides being an informative insider's account of those extraordinary times, Teller's memoirs are also valuable as the personal account of a man who pursued the two-fold Baconian vision in its starkest form: to probe the fundamental nature of physical reality and to bring into the world devastating weapons of mass destruction.

Edward Teller was born in Budapest in 1908. His early years are notable chiefly for the friendships he formed with three other young Hungarians, all of them destined to become world-famous physicists who aided the Manhattan Project in decisive ways: Eugene Wigner, John von Neumann and Leo Szilard. The four friends, all of them Jewish, were destined to immigrate to the United States, fleeing European anti-semitism in general and the Nazis in particular. It is, of course, one of history's great ironies that Hitler's persecution of the Jews led to a vast intellectual westward migration, chiefly but not exclusively Jewish, which, among its other effects, greatly enhanced the intellectual firepower of the Allied war effort.

Teller recounts his early experiences as a young theorist in the heady days of the birth of quantum mechanics. As with so many young physicists of the time, Teller's early career consisted mainly of an itinerant apprenticeship at the great scientific centers of Europe. Teller earned his doctorate under Werner Heisenberg in Leipzig, worked with Carl Friedrich von Weizsäcker in Göttingen, and studied with Niels Bohr in Copenhagen. In 1932 he paid a memorable visit to Rome where he began a lifelong friendship with Enrico Fermi who, among many brilliant achievements, was the first to produce radioactive elements by bombarding uranium with neutrons. Without quite realizing it, Fermi had in 1932 discovered nuclear fission-the splitting of uranium atoms into atoms of other elements, accompanied by the conversion of mass into energy. The nuclear age was at hand.

Before leaving Europe permanently for the United States in 1935, Teller spent a year at the University of London. It was at that time that Leo Szilard proposed that the bombardment of nuclei by neutrons might release additional neutrons as well as radiant energy, thereby initiating a chain reaction that could result in a powerful explosion. Szilard shared his idea with Teller, who recalls having found it "interesting, frightening, and logical."

Prior to World War II, Teller spent six years as a professor at the George Washington University. These years were marked by frequent contact and collaboration with other great physicists who had emigrated from Europe to escape Hitler and the coming war, including Fermi, Bohr, Szilard, Wigner, George Gamow and Hans Bethe. In 1939, Werner Heisenberg visited Teller in Washington. When Teller asked Heisenberg why he would not stay in the United States, Heisenberg answered, "Even if my brother steals a silver spoon, he is still my brother."

Heisenberg was to spend the war years as the outstanding physicist in Nazi Germany and, it now seems clear, as the scientific leader of the German effort to achieve the atom bomb. In February 2002, letters written to Heisenberg after the war by Bohr-but never sent-were made public, documenting Bohr's claim that Heisenberg had devoted himself with enthusiasm to the Nazi bomb project. At issue was a visit paid by Heisenberg and von Weizsäcker to Bohr in occupied Copenhagen in 1941, an incident now famous as the subject of Michael Frayn's hit play, Copenhagen. According to Bohr, at their meeting Heisenberg expressed his confidence that Germany would win the war and revealed that he had been working on the atom bomb more or less exclusively for the past two years. Heisenberg himself, after the war, claimed to have done what he could to prevent the development of an atom bomb in Germany. As for Teller, he has insisted from the start of the controversy that Heisenberg never had his heart in the work and that, to the extent that he labored, he labored as one forced. "I could not imagine", writes Teller, "that he would support the Nazis willingly, much less do so enthusiastically."

At a 1939 Washington conference on theoretical physics, Bohr announced that two chemists in Germany, Otto Hahn and Fritz Strassman, had shown that neutron bombardment can split uranium into lighter elements, with the release of energy and other particles. Nuclear fission, which Fermi had observed without interpreting it correctly, was now an established fact. Once again it was Szilard who drew the practical implications: if the fission process produced additional neutrons, initiating a chain reaction, then both nuclear energy and nuclear explosions would be feasible. The release of extra neutrons was soon confirmed experimentally. Szilard, Teller and Bohr quickly realized that nuclear fission could have profound military implications, particularly in light of the looming threat from Nazi Germany.

Szilard drafted a letter to President Roosevelt alerting him to the possibility of a fission weapon. He felt the letter would have more weight with Roosevelt if it were signed by the most famous physicist of the time, Albert Einstein. On a memorable August day in 1939, Teller drove Szilard to Long Island to visit Einstein in his summer home. Einstein signed Szilard's letter, which foretold "extremely powerful bombs of a new type" and urged the President to fund nuclear research and to maintain "permanent contact between the Administration and the group of physicists working on chain reaction in America." Having read the letter, Roosevelt at once set up an Advisory Committee on Uranium. At its first meeting, Teller asked for and was granted $6,000 to purchase graphite to construct an experimental nuclear reactor. Such were the modest beginnings of the Manhattan Project which, with the help of ten thousand people and the expenditure of $2 billion, produced the world's first atom bomb in 1945.

It is astonishing to reflect on how little time passed between Bohr's 1939 announcement of nuclear fission and the first successful test of the atom bomb in 1945. The Manhattan Project was carried out first at Columbia University and the University of Chicago, and later at a new laboratory established at Los Alamos, New Mexico. J. Robert Oppenheimer, a physicist recruited from the University of California at Berkeley, led the Los Alamos team. Teller, along with Bethe and von Neumann, was involved in much of the theoretical work of designing a fission bomb, and his account of that time is a valuable addition to the literature on the Manhattan Project. But from the beginning Teller was also an enthusiastic proponent of work on a fusion or thermonuclear weapon.

In an atom or fission bomb, the splitting of the uranium atom after it is struck by a neutron releases other neutrons in addition to a large quantity of energy. If a sufficient amount (or critical mass) of uranium is present, these other neutrons cause the fission of other uranium atoms, thereby initiating a chain reaction. Typically, two subcritical masses of uranium are kept apart until just before detonation; the size of a fission bomb is thus limited by the need, for safety's sake, to keep the quantity of uranium subcritical prior to detonation. In a hydrogen or fusion bomb, the main energy comes from the fusion of heavy hydrogen into helium. A hydrogen bomb is actually composed of a small fission bomb and a much larger fusion bomb; the tremendous heat generated by the fission device triggers the chain reaction of hydrogen fusion. Because of its two-stage design, a hydrogen bomb is also known as a thermonuclear weapon. With no restrictions as to critical mass, the size of a hydrogen bomb is virtually unlimited.

The thermonuclear bomb originated in the mind of Enrico Fermi in 1941. Initially, Teller himself was skeptical that a fission device could produce sufficient heat to create fusion. Fusion will not begin at temperatures lower than 50 million degrees, a condition found only at the center of stars like our sun. In any event, work on the fusion bomb-nicknamed "the Super" at Los Alamos-languished during the race to produce the atom bomb. The first such bomb (code name: Trinity) was tested successfully in July 1945, to be followed within a month by the dropping of atom bombs on Hiroshima and Nagasaki.

After the surrender of Japan, many of the senior scientists involved in the Manhattan Project wished to end their involvement in weapons research and return both to theoretical physics and to their normal lives. Oppenheimer declared that "with the war over, there is no reason to continue work on the hydrogen bomb." As for the Los Alamos laboratory, according to Teller, Oppenheimer said, "Give it back to the Indians." As Teller describes it, the attitude of most physicists reflected their revulsion after the use of the atom bomb on Japan and their optimism that, with the peace established in 1945, nuclear weapons research would be unnecessary. Bohr's view was typical: War in the nuclear age, because of its destructiveness, had become impossible. Therefore, scientists should no longer work on weapons. Teller found these opinions naive and unrealistic, and he was soon proved correct.

The Soviet Union exploded its first atom bomb in 1949, thanks in part to information supplied by Klaus Fuchs, a Communist spy at Los Alamos. If the hydrogen bomb were feasible, there was no doubt that the Soviets under Stalin would seek to develop it; Teller and others were therefore more determined than ever to press ahead with the American thermonuclear program. But Teller faced impassioned resistance from other physicists who seemed to believe that if we did not pursue the hydrogen bomb, then neither would the Soviets.

In January 1950, shortly after Fuchs' arrest for espionage, President Truman announced his decision to continue work on all forms of nuclear weapons, including the hydrogen bomb. Thus it was that, after a delay of some years, Teller could once more devote himself energetically to the thermonuclear program with the full support of the U.S. government, if not that of the majority of American physicists. Teller's account of this work is especially absorbing. The huge calculations required were performed with the aid of the world's first computing machines, designed by Teller's brilliant friend John von Neumann. The key breakthrough was an insight, due partly to Teller and partly to the mathematician Stanislaw Ulam, that fusion would commence if the fission explosion were used not only to heat the heavy hydrogen but also to compress it to a high density. The relative contributions of Teller and Ulam are still hotly disputed, and Teller's treatment of this subject is not perhaps definitive. In any event, on the basis of the Teller-Ulam configuration, and crucial calculations provided by Richard Garwin, a thermonuclear bomb was successfully exploded in 1952. The Soviets exploded their own thermonuclear bomb in 1955, and so began in earnest the era of uneasy peace preserved by the threat of mutually assured destruction.

In the years after the achievement of the hydrogen bomb, Teller continued to play a leading role in formulating American policy on nuclear energy and weapons research. Most importantly, along with Ernest Lawrence at Berkeley, Teller persuaded the government to create a second national laboratory for nuclear weapons research in Livermore, California. Teller was also active in setting rules for the safety of nuclear reactors and in promoting advanced education in the field of "applied science", a sort of hybrid of engineering and theoretical physics.

Nonetheless, in the minds of most American physicists today and a good part of the educated public, as well, Edward Teller remains a sinister figure, somehow epitomizing in his person all that is morally suspect about the Cold War, atomic energy, and nuclear weapons. Indeed, Teller is generally taken to be one of four possible models (with Werner von Braun, Herman Kahn and Henry Kissinger) for Stanley Kubrick's unforgettable character Dr. Strangelove, played brilliantly by Peter Sellers in the 1964 film. In part, this is attributable to Teller's incessant promotion of the hydrogen bomb, his unpopular advocacy of peacetime uses for nuclear explosions (to dig harbors and canals, for example), his skepticism toward arms control, and, during the Reagan presidency, his role in promoting the Strategic Defense Initiative. Of course, in this last respect, the contempt heaped on Teller mirrors the fate of nearly every prominent public intellectual who dared to deviate from the prevailing liberal orthodoxy, especially in the last decades of the Cold War.

But Teller has also been particularly despised and shunned for his supposed role in the "downfall" of J. Robert Oppenheimer, whose security clearance was revoked by the Atomic Energy Commission following hearings in 1954. Oppenheimer was charged with harboring Communist sympathies; he was stripped of his clearance in part because of Teller's adverse testimony. Many physicists have never forgiven Teller for what seemed to them an act of treachery against a brilliant colleague who had, after all, guided the Manhattan Project to its triumphant success. It was easy enough to conclude that the long-running tension between Teller and Oppenheimer over whether to pursue the hydrogen bomb was the real reason Teller was willing to help destroy his former boss's reputation.

This is a complex and difficult subject, however, and one on which Teller's memoirs do shed some interesting light. (Teller's complete testimony is included as an appendix to the book.) While Oppenheimer was certainly no Soviet agent, he was, in his own words, "a member of just about every Communist Front organization on the West Coast." He also committed serious indiscretions and recklessly lied to federal investigators, actions for which he might have lost his clearance even without Teller's testimony. As for his own role, Teller clearly indicates that he regrets his decision to testify against Oppenheimer, that he admired him immensely, and that, in his testimony, he questioned only his colleague's judgment and never his loyalty. In any case, since Oppenheimer retained his post as director of Princeton's Institute for Advanced Study, one should not exaggerate the injury done to him by the suspension of his security clearance.

On the whole, it seems clear that the vilification Teller has endured is largely unmerited; that for decades he worked tirelessly and devotedly on behalf of his adopted country; that he made immeasurable contributions to American national security; and that, in all likelihood, the hydrogen bomb he bequeathed to the world has helped, by its deterrent effect, to maintain the relative peace the world enjoyed during the latter half of the 20th century. For these lasting achievements, Edward Teller, that supreme practitioner of Baconian science, deserves our admiration and our gratitude.

Adam Schulman teaches the liberal arts at St. John's College in Annapolis, Maryland.