Linus Pauling was a chemist, peace campaigner, and double Nobel Laureate who played a central role in two great unifying projects of twentieth-century science.

Born in Oregon, U.S.A., in 1901, Pauling worked his way through college, receiving a BS in chemistry from Oregon Agricultural College in 1922. There he read papers on valence by physical chemists G. N. Lewis and Irving Langmuir, sparking his interest in the theory of chemical structure and bonding. He moved to California Institute of Technology (Caltech) for doctoral work on X-ray studies of inorganic crystal structures and had published twelve papers by the time he graduated in 1925. In 1926 he traveled to Europe on a Guggenheim postdoctoral fellowship, visiting Munich and other centers of the new quantum mechanics. On his return from Europe, Pauling resumed his work on X-ray crystallography, developing what he later called his chemical intuition about possible...