After World War II, in a world under the shadow of nuclear devastation, nuclear energy found many beneficial uses. The first nuclear power plant began operation in 1957. Radioactive isotopes became extremely useful in the diagnosis and treatment of many medical conditions. But the balance between the pros and cons of nuclear technology is difficult to determine. In the early twenty-first century, Great Britain, France, China, India, and Pakistan possess nuclear weapons. Undoubtedly many more nations will acquire them. Despite the nuclear arms reduction agreements between the United States and Russia, the spread of these weapons of mass destruction has increased. Nuclear energy is now a global resource, and its use for good or ill is felt by all humankind. As Secretary of War Stimson wrote in 1946, "The focus of the problem does not lie in the atom; it resides in the hearts...