Keeper of the Nuclear Conscience: The Life and Work of Joseph Rotblat.

Many of the scientists who worked on the Manhattan Project, America's programme to build an atom bomb during the second world war, had misgivings about their work. After the detonation of the first test bomb in 1945, Robert Oppenheimer, the programme's director, later claimed to have recalled a line from Hindu scripture: “I am become death, destroyer of worlds.” His colleague Kenneth Bainbridge was pithier: “now we're all sons of bitches,” he muttered.

Joseph Rotblat, a Polish-born physicist, had stronger reservations than most. He had been disturbed to overhear the American general in charge of the project admit that the real point was not to pre-empt the Nazis—whose own atomic-bomb project had got nowhere—but to intimidate the Soviets, the Americans' wartime allies. In 1944 Rotblat left the programme to return to Britain, where he had taken refuge from occupied Poland, and resolved to put his expertise to more humane use. He swapped theoretical physics for the medical kind and began a life of vigorous opposition to nuclear weapons. A friendship with Bertrand Russell, a British philosopher, led to the founding of the Pugwash conferences on nuclear disarmament.

Andrew Brown's biography traces the history of both Rotblat as a man and Pugwash as a group. That dual focus is occasionally jarring—at one stage he moves from a discussion about test animals in Rotblat's London hospital to a sweeping history of attempts to ban nuclear testing. Acronyms, committees and minor players come thick and fast. Readers can expect to make frequent trips to Wikipedia.

But the story itself is good enough to shine through. The idea behind Pugwash (named for the remote hamlet in Nova Scotia where the early meetings were held) was that scientists—particularly nuclear scientists—were uniquely suited to grapple with the problems of the nuclear-armed world which they had helped bring into being. They understood the details and were prone to thinking bold thoughts. As an international scientific group, Pugwash was a useful counterpart to the fearful nationalism shaping politics. Delegates debated the theory of nuclear deterrence, pondered the potential damage of a nuclear war, and agitated for disarmament and the abolition of nuclear weapons.

Many of the attendees had the ear of their national governments. Over the years the Pugwash conferences evolved into a crucial source of backdoor communications between the superpowers, penetrating the fog of mistrust that characterised the cold war. The foundation of the Partial Test Ban Treaty (which banned aboveground nuclear explosions) and various other nuclear disarmament treaties was laid largely at Pugwash.

For Rotblat, though, these were only partial victories. Throughout his life, his goal remained a world free of nuclear weapons. His experience of the second world war had a lasting impact (his wife may have been murdered at Belzec, an early Nazi death camp). He was not convinced by the argument that the threat of nuclear weapons would ultimately prevent war. The logic of deterrence, and later of mutually assured destruction—which presumes that war between nuclear-armed nations is impossible, because the mutual annihilation ensures that neither side could win—applies only to rational actors. Had Hitler had the bomb, Rotblat argued, “his last order from the bunker in April 1945 would have been to use it on London even if it meant terrible retribution to Germany. This would have been part of his philosophy of Gotterdammerung.”

Readers may now find Rotblat's idealism naive. Talk of total nuclear disarmament seems idle in a world with nine nuclear powers and a simmering crisis over a possible tenth. Yet the pessimism of the 1950s has proved overblown as well: nuclear weapons have proliferated much more slowly than many feared at the dawn of the atomic age, and stockpiles have dwindled since the height of the cold war. For Rotblat, to be accused of idealism was no bad thing. He liked to quote his friend Russell: “do not fear to be eccentric in opinion, for every opinion now accepted was once eccentric.”