Three years ago, 48% of us voted Remain. If another vote were taken in the near future, the figure would probably top 50%. But perish the current leading politician or businessperson who makes the case for ongoing membership of this remarkable international organisation on our doorstep. Apart from a few outliers, it is taken as a political given that Britain must leave the EU; the divisive question is in what form.

For although the focus is largely on the undoubted deleterious economic impact – the worse the harder the Brexit – the bigger question is what country do we want to be. The EU has rightly become the talismanic issue of our times.

For if you support EU membership, you will tend to own a cluster of other values and principles. You recognise that today’s economies and societies are interdependent and that it’s imperative to have institutions to manage those interdependencies, whether on climate change or the overarching power of the new technopolists. You are not instinctively distrustful, even hostile, to other cultures, languages and peoples: you find diversity attractive and enriching. You are for openness and tolerance. While proud of your country, you do not see that pride compromised by working with and alongside other countries and peoples.

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You do not believe in capitalism red in tooth and claw; you see the case for stakeholder capitalism, for the regulation of finance and for using state power to promote competition and innovation. You celebrate the role of trade unions in giving employees voice and vital countervailing power. You do not regard low taxation as the be-all and end-all of public policy. You uphold the values behind a social contract in which members of society accept mutual rights and obligations, so sustaining strong public health and education and social insurance that supplies income in adversity or old age. You believe in strong public institutions, ranging from the BBC to museums, which so enrich our country.

Propounding EU membership is thus a civilisational proposition. It does not mean that you regard every aspect of the EU – its unsigned-off accounts or the intricacies of the common agricultural policy – as perfect. But then neither is every aspect of the UK. But it does mean that you sign up for a set of interlocking propositions, shared by other Europeans, which better allow people to live lives they have reason to value.

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Standing in opposition is a very different set of values and principles. To want to leave is to deny international interdependencies in order to assert national “control”. You reject mutuality of international obligation and the necessary pooling of sovereignty and sharing of law and resource to achieve common ends that would otherwise be impossible. Rather, the moral injunction for state and individual alike is to stand alone and act solely in your own interests. The EU is a hostile “other”: it spends our money and sets objectionable regulations, although when challenged, no regulation can be cited whose aim can reasonably be contested. Small wonder; they reflect the will not just of the British parliament, but of the parliaments of Europe.

You object to the EU’s openness – to trade, ideas and people – especially to European citizens who can live and work in Britain as of right. It matters not that the British have equal rights: who would want to have the right to leave their homeland to become a citizen of anywhere? At the limit, you can only trust your own, who share the “indigenous” culture and love of home; those from other cultures, who speak other languages and worship other religions, are the alien other whose presence is necessarily the principal cause of your own and wider society’s ills.

Brexit is thus a parallel civilisational proposition – to create a world of closure, intolerance and suspicion of the other. Economically, this will express itself as less trade, less inward investment and less growth – and reduced capacity to work with other countries to confront common challenges. But that is less the point than the impact on our civilisation. We will become more intolerant, more mean spirited, accelerating the trends already clear since the referendum. We will be ever more suspicious and hostile to people of colour, the European, the Jew and the Muslim. We will contract and be diminished.

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Thus the “vox pop” calls from the bluff Yorkshire pensioner or Essex white-van driver to get on with Brexit or parallel calls from their MPS to respect the “will of the people” cannot be tamely and mutely accepted. I don’t believe that the mass of the British want to embrace the choice Brexit represents or that those who voted Leave hold views that are immutable. They are fellow Brits and fellow Europeans who have fallen prey to callow leaders and trash populist argument. It may be that Theresa May gets a narrow majority on the third or fourth time of asking for her “ deal”. But while trying to limit the economic damage, this will end up with Britain having the worst of all worlds – tracking the EU without influencing it, while embracing closure.

But whatever the deal, the civilisational challenge cannot be dodged. I do not want to live in the kind of country that Brexit is creating and I believe a majority share that view. If we leave, millions of us will seek to convert our fellow citizens and remind them that so much of what goes to make us British has roots in very different values from those feeding Brexit.

Above all, we will look to leaders, so sadly absent in our two main political parties, who lead and form public opinion, instead of following what they imagine it to be. We did not want or choose this battle. But now it is upon us, we have to take up the peaceful arms of persuasion, words and argument – and fight to win it.

• Will Hutton is an Observer columnist