As football fever envelops the planet, with all eyes turned towards Brazil, I want you to imagine a different World Cup. Each country sends their national team as usual, but then all the players are pooled together and divided into teams based on their astrological star sign. So Virgos play Leos, and Aquarians are pitted against Aries, with each team having players from a mix of countries. Who would win overall? Perhaps the power of Taurus, the bull, would be no match for the sharp sting of Scorpio. We might imagine other World Cups, where teams are based on shoe size – the clodhopping size elevens against the nimble-toed eights – or maybe the favourite colour of each player.

If this sounds ridiculous, it is no more absurd than dividing teams on the basis of something as arbitrary as the nationality of the players. This strange practice involves determining team members by where they happen to have been born on a particular land mass, which citizenship document they have managed to get hold of, and where the national frontier is at the time of play.

We should remember that nation-states are historical inventions, mainly emerging since the eighteenth century. Only one hundred and fifty years ago, there was no such thing as Germany or Italy; these states were an agglomeration of principalities. Bosnia and Herzegovina’s team would not be battling for supremacy in Group F if it had not been for the break-up of the former Yugoslavia in the 1990s.

The artificiality goes further, in the sense that every country has relied on a barrage of invented traditions and other propaganda devices to generate its national identity. The Scots – who failed to qualify for Brazil 2014 – take pride in their apparently ancient Highland dress, but according to the historian Hugh Trevor-Roper, the wearing of ‘traditional’ kilts and tartans was an invention of the mid-eighteenth century, partly as a protest against the Union with England.

Similarly, the English are so proud of their red-on-white St George’s Cross, which I see fluttering out of windows and tied to car aerials in the town where I live. But few people realise that St George himself was born in Palestine in the third century, and that the flag was already in use in the fifth century by the Georgian King Vakhtang Gorgasali. Children in the United States have national pride injected into them in school every morning when they swear allegiance to the country’s flag. No community is more deeply imagined than the nation-state.

None of this would really matter if nations were innocent actors on the world stage, but we know that this is not the case. There have been no major wars between armies representing different signs of the zodiac. When it comes to warfare in the past century, nationalism reigns as the supreme culprit. From the two world wars to the conflicts in Yugoslavia and the violence that has recently flared up in Ukraine, nationalism has been one of the most destructive forces in modern human affairs.

How does this all relate to football? In some ways football tournaments like the World Cup – and sport more generally – can encourage a healthy form of nationalism that forges unity in countries with significant social divides. Brazil may be plagued by severe wealth inequality and deep racism, but its disparate citizens rally together to support their national team. South Africa found that holding the Rugby World Cup in 1995 helped create a unified national consciousness and heal the wounds of apartheid, generating empathy between black and white.

But football also plays a role of legitimising and exacerbating divisions between nations. This is not simply visible in the extreme form of hooliganism, but in the more everyday way that people generally support their national team, rather than those of rival nations. Football, like national flags, is part of the ideology that generates the distinctions between ‘us’ and ‘them’, which ultimately cause so much violent conflict and human suffering. As the sociologist Richard Sennett has written, ‘we’ is a dangerous pronoun, since it necessarily involves the ideas both of inclusion and exclusion. Shouting for your own team also means not shouting for the opposition.

I can appreciate that football is much more about skill and beauty than about creating dangerous forms of nationalism (in fact, the beauty of sport is a central theme in my book The First Beautiful Game). Football also has the capacity to replace violence with a more gentle ‘war by other means’ – kicking a ball around on some grass. But nationalism has a history of being a dark force, and we should make our best efforts to erode its power and presence. So if you are about to watch your national team play in Brazil, at least consider giving your support to the opposition. In the end, however, we would be much better off with a World Cup that was based on star signs or shoe size rather than nation-states.

This is a slightly edited version of an article that I wrote four years ago during the World Cup in South Africa.

I discuss the invention of nationalist traditions and how they shape our beliefs in my book The Wonderbox: Curious Histories of How to Live.