When did the first institutional forms of contemporary European unity emerge? There are essentially two approaches to answering this question. The first is to take the perspective of poets, writers and intellectuals. The second is to consider the projects and achievements of politicians. If we take the first approach, we must refer to all thinkers of European consciousness who imagined European unity, from the Abbé de Saint-Pierre and Victor Hugo to Émile Mayrisch and, more recently, Stefan Zweig. If we take the second, we must focus instead on institutional forms of unity, the ways in which citizens participate in it, and then assess its effects. We must present the most effective agents of unity, and explain their reasons for taking action.