Linus Pauling loved science. He did not love political work. He once gave an interview in which he referred to his peace activism as "something that I didn’t care to do very much, except for reasons of morality and conviction." In the end, he won the Peace Prize, which he viewed as a vindication of this difficult work. But what impact did Pauling’s peace work really have? During the decade and a half between 1948 and 1963, a time during which the governments of the world were grappling for the first time with the challenges of proliferating nuclear weapons, Pauling, Einstein, and Bertrand Russell rose to become the world’s three most visible and influential peace activists.

But there were important differences between Einstein and Russell on one hand, who were, in their own ways, philosophers of peace, and Pauling, more of a hands-on activist. He did not merely lend his name to advertisements and pen declarations. Pauling marched, picketed, debated, wrote scores of letters to publications, spoke hundreds of times. He organized global meetings. He met with world leaders. He knew how to time and present his views in ways that garnered the greatest possible amount of media coverage. He could speak to large groups with passion, and was a rare scientist who could mobilize a crowd. His kitchen-table petitions against the spread of nuclear weapons were critical in demonstrating that scientists worldwide were anti-Bomb. He helped make dissent during the McCarthy era both rational and respectable.

Pauling was different in a deeper way as well. Einstein and Russell did their peace work at the ends of their careers, when they were so eminent they had little to lose by taking unpopular political stands. They were untouchable. Pauling, however, risked a great deal. He could -- and did -- lose research funds and prestige within his field, and lost the chairmanship of his division at Caltech. Years of attacks in the press and by government officials left him stained for the rest of his life, seen by many as more a crank than a genius. His political activism thereby became something more than a gentleman’s act of conscience. It was an act of surpassing courage.