He believes (as do former Secretaries of State Henry Kissinger and George Shultz, former Secretary of Defense William Perry, and former Senator Sam Nunn) that unless the world finds a way to live without nuclear weapons, we will find ourselves in an international system in which 30-50 states possess them, raising the danger of accidental or deliberate launch to an unacceptably high level. Convincing great powers to eliminate their nuclear arsenals might seem as politically fanciful as pushing gun-control legislation through the US Congress, but on that issue, too, Obama has made clear that he is willing to try.