The author is a Reuters Breakingviews columnist. The opinions expressed are his own.

Until about five years ago, I didn’t give much thought to whether Britain should stay in the European Union – because quitting didn’t seem like a realistic prospect. Insofar as I did consider the matter, I had a vague feeling that we were better off in than out – but knew I would need to delve into the topic to understand why that was so.

In the early part of the century, I was too busy setting up Breakingviews to do this. Our initial focus was on the dotcom bubble and corporate finance. We didn’t do much macroeconomics, let alone politics. For example, we sat out of the debate over whether Britain should join the euro.

But during the credit bubble, our focus changed. We worried that the financial system was getting over-leveraged. When the crunch actually came, the story became banks, macro and crisis – and the political response to all that.

The credit crunch mutated into the euro crisis – during the early days of which we sold Breakingviews to Thomson Reuters. I immersed myself in the Greek crisis. I now saw myself as a political economist rather than a financial journalist.

Freed of a day job, I also wrote a book about whether we should stay in the EU. After David Cameron declared himself in favour of a referendum during a speech in January 2013, it was clear that this was going to be the big political issue of the coming years.

My initial focus was on the economic arguments – in particular, the line that we could stay in the single market while quitting the EU. But the more I examined it, the more I realised that none of the alternatives for trading with the EU – such as the Norwegian and Swiss options – were any good. They involved less access to the single market, while moving from being a rule-maker to a rule-taker.

I also became aware of the ghastly phrase, “non-tariff barriers” – the panoply of regulations that gum up trade, especially in services. The EU’s original common market was about removing tariffs. The move to create a single market since 1992 has been about dismantling non-tariff barriers. Trade liberalisation in the 21st Century will be almost entirely about further getting rid of rules that stop commerce because most tariffs have already gone.

The more I thought about this, the more I realised how Britain, whose economy is 80 percent services, has a huge amount to gain from EU projects like capital markets union and the digital single market. These will extend the single market to the liveliest industries of the future, where Britain excels.

We’d also be hurt if we lose full access to the single market. For example, the City would no longer have a passport to operate freely across the EU. It would suddenly face a massive “non-tariff” barrier.

I still think the economic case for staying in the EU is powerful. But over the past year or so, geopolitical considerations have played an even bigger role in my thinking. Consider the boiling cauldron of the Middle East and North Africa. Unless we find a way of stabilising this region, Europe will be troubled too. We can’t just pull up an imaginary drawbridge.

The idea that Britain can do anything useful about this if we quit the EU is pie in the sky. Surely we have learnt – from our wars in Iraq and Libya, and from Angela Merkel’s unilateral offer to Syrians to come to Germany – that when Europe is divided, our interventions will cause more trouble than good.

There’s even a risk that Brexit will lead to the breakup of both the UK, with Scotland going its own way, and the EU. How can that make us safer and stronger? The possibility that Donald Trump, an anti-NATO bully, may be the next U.S. president makes me all the more keen to stay in the EU.

By contrast, if we remain, we can be one of the EU’s leaders. We can help devise a joined up economic and political plan to settle the Middle East and North Africa. There are no quick fixes. But surely we must try.

As the referendum campaign has progressed, another consideration has weighed on me. The Leave camp has been running a campaign of misinformation – telling the voters that we send £350 million a week to Brussels – when we don’t – and that Turkey is scheduled to join the EU in 2020 – when it isn’t.

If Britain votes to leave, post-truth politics will have triumphed – polluting our democracy. We must fight that with every sinew.