In times when the temptation of exclusion is again present, this book presents the works of various scholars, philosophers, politicians and lawyers, all visionaries who, nearly four centuries ago, had the conviction that unity is force or rather, peace. They proposed the rulers of States? Mainly Europeans? various plans and projects perpetual peace, in which they faced the dilemmas of his time, dilemmas, with some surprise, discovered contemporaries. The geographical definition of Europe is variable throughout the project, just as in the twenty-first century, we have not solved the problem of the borders of Europe in the framework of the European Union. Also, the first wave of projects is indebted to the religious wars that ravaged Europe, and religious conflicts are, in today's global society, a new test for religious freedom claimed in many of these projects alone. The lust for power of states in international relations, the origin of many of these writings, but did not cause interstate wars on European soil for more than half a century, yes it has caused division in the weak and incipient foreign policy Union. Ultimately, beyond the specific legal and constitutional structures proposed, ranging from the establishment of an EU court to the creation of the 'European Leviathan, "that is, of a true United States of Europe, these works speak of an "original sin" of the human being: constitutionalism, ie, the desire to control the power and limit its exercise, avoiding the risks of a legibus solutus power.