AP Photo

While we Europeans should redouble our efforts to ensure that our continent does not forget its troubled past, the need for scale is the key to our shared future. The 21st-century world will be one of giants: weary old ones, like the United States and Russia, and hungry new ones, like China, India, Brazil and South Africa. You do not need to accept the most apocalyptic forecasts of European decline to acknowledge that Europe is unlikely to remain the world’s largest economy for long. In such a world, even Germany will be a small- to medium-size power.