When the American Founding Fathers set about the task of perfecting the constitution of their union, they turned to the theory and practice of the Old World for counsel and illustration. The Federalist Papers contain many references to Hume and Montesquieu, the British Constitution and ancient leagues. However, it was not copying from foreign examples that made such an outstanding success of the Constitution of the United States. Rather it was the authors' imaginative creativity that gave to this oldest of the still operating written constitutions its unique combination of stability and flexibility, effectiveness and efficiency.