Three years ago, I traveled to Prague and I declared America’s commitment to stopping the spread of nuclear weapons and to seeking a world without them. I said I knew that this goal would not be reached quickly, perhaps not in my lifetime, but I knew we had to begin, with concrete steps. And in your generation, I see the spirit we need in this endeavor -- an optimism that beats in the hearts of so many young people around the world. It’s that refusal to accept the world as it is, the imagination to see the world as it ought to be, and the courage to turn that vision into reality. So today, with you, I want to take stock of our journey and chart our next steps.