AP Photo

As leaders of the G-8 industrialized countries gather at Camp David later this week, there will be much talk of global leadership -- and of its importance for our crisis-prone world. In a world where so many challenges transcend borders -- threats to the stability of the global economy, climate change, cyberconflict, terrorism, and risks to reliable supplies of food and water, to name just a few -- the need for international cooperation has never been greater. Yet, cooperation depends on leadership. Only global leaders have the leverage to coordinate multinational responses to transnational problems, as well as the wealth and power to persuade other governments to take actions they would not otherwise take. They provide services no one else will pay for and resources that...