Foreign policy experts often refer to the system of institutions, alliances, and norms built up after World War II as “architecture.” We still needed a rules-based global order that could manage interactions between states, protect fundamental freedoms, and mobilize common action. But it would have to be more flexible and inclusive than before. I came to liken the old architecture to the Parthenon in Greece, with clean lines and clear rules. The pillars holding it up— a handful of big institutions, alliances, and treaties— were remarkably sturdy. But time takes its toll, even on the greatest of edifices, and now we needed a new architecture for a new world, more in the spirit of Frank Gehry than formal Greek classicism. Where once a few strong columns could hold up the weight of the world, now a dynamic mix of materials, shapes, and structures was needed.