A united Europe was not the invention of pragmatic politicians after WWII. Instead, the idea of a Europe united dates back to the times of Greece and Rome, of Alexander and Caesar Augustus, who believed in uniting the continent under the pillars of their respective societies; their language, culture, religion and currency.
A united continent was put on hold following the collapse of the Western Empire in 473CE but became a popular subject around the Renaissance period in the 15th century, particularly in Italian cities such as Florence, Venice, Milan and Bologna, where Greco-Roman ideals were re-discovered and idealised by philosophers, artists, politicians and merchants alike. The use of Latin as a common intellectual language (Newton wrote his Principia in it) and the trans-European friendships of Renaissance humanists such as Erasmus and Thomas More all show how the contemporary belief in a united Europe is actually a direct continuation of the Renaissance.
Let’s of course not forget about the great Charlemagne. Charlemagne's achievement was the realisation of a united Europe. There were no wars except at the frontiers. It was only the “stable society created by Charlemagne” that allowed for an “extraordinary outpouring of cultural, artistic and intellectual activity”, according to French historian Jacques Boussard in “The Civilisation of Charlemagne” (1968).
The Enlightenment era saw a flourishing of “One Continent” ideals. Napoleon Bonaparte believed strongly that the monarchies of Europe, quibbling over lands and riches for centuries whilst doing everything to remain isolated and nationally-egoistic were limiting the potential of their nations and their people. Bonaparte, though authoritarian and uniting Europe by force, once remarked “Europe thus divided into nationalities freely formed and free internally, peace between States would have become easier: the United States of Europe would become a possibility." He went on to say, "I wished to found a European system, a European Code of Laws, a European judiciary: there would be but one people in Europe."
This idea of "the United States of Europe" was one later picked up by many others throughout history. There was Pierre Dubois, a counsellor for the Duke of Burgundy, who called for a European federation in 1306; Immanuel Kant, the German philosopher who made a celebrated call for “perpetual peace”; William Penn, the founder of Pennsylvania, and an early advocate of a European parliament; and Victor Hugo, the French 19th-century novelist who proclaimed in 1849 that “A day will come when you, France, you, Russia, you, Italy, you, Germany, you, all nations of the continent, without losing your distinctive qualities and glorious individuality, will be merged within a superior unit.” Winston Churchill, idolised by eurosceptics today, was a fervent believer in a closely integrated Europe after WWII to make the continent dependent on its nations cooperating and trading with one another as if they were one body.
That is why Brexit and national egoism in Europe today is an anathema to the history and culture of Europeans. With so much culture, language, religion and history condensed in such a closely-situated geographic area- and of course much of the culture, language, religion and history overlaps as you cross into different nations- it only makes sense for the continent to be united. After centuries of war, particularly the first half of the 20th century where nationalism brought Europe to the brink and led to tens of millions being killed in conflict. European unity is both the best way of guaranteeing peace in Europe and a natural historical progression.
Europe today is undergoing significant political and societal change, as evidenced by the national elections in the Netherlands and France, and the Alternativ für Deutschland’s strong 3rd placed showing in the German federal elections on Sunday. Nationalism is on the rise in Poland and Hungary, and Brexit shows that certain countries want to move integration backwards, not forwards. In all, however, the European Union has brought unparalleled peace and prosperity to a continent where such characteristics were rare for most people. The Union has brought societies closer than ever and made the continent inter-connected and trade dependent. Economic, education, environmental and digital integration has made Europe the most competitive economic area on earth and freedom of movement has made Europeans, once separated by walls and borders, neighbours regardless of their location or language.
The rest of the world has much to learn from the European Project. Perhaps a similar arrangement could be possible between the United States and Canada, or between certain Latin American countries. Europe is an idea, not just a geographic accident, and though some may try to see the progress reversed, the dream of a United Europe lives on.