THERE is an old chess short story about the grand master who ends up in a remote village. Short of money, he agrees to play two locals; his meal will be free if he wins both matches. But there is a catch; in one game, he must play as white, in the other as black. As soon as the matches start, he realises his mistake when the man playing white in the second game simply copies the grand master's moves as white in the first. No matter what the master does, he cannot win both games; if he wins in the first, he must lose in the second.

The three-way negotiations between Britain, the European Union and Scotland could yet work out the same way. Every argument used by Theresa May against the EU can be used against her by Nicola Sturgeon.

Taking back control. The Leave campaign clearly resonated with voters when it talked about the need for Britain to take back control of its laws from a remote Brussels bureaucracy. But the argument applies just as well in Scotland where the Conservatives last won most seats in 1955; in the 2010 and 2015 elections, the Tories got one seat but the Scots still ended up with a Conservative prime minister. It will probably happen in 2020 as well. Do the Scots have influence anyway? Well, they have asked for a deal in which Scotland stays part of the single market; Mrs May is refusing to ask for such a deal.

Economic forecasts are too gloomy. Most economists and think-tanks thought Britain would be worse off when it left the EU. The Brexiteers argued that this was "project fear"; so far, the British economy has been doing fine since the referendum (although sterling has plunged). The same arguments will be applied in Scotland and had some success in the first referendum in 2014. But Scots may take courage from the British example. And there has just been a billion-barrel oil discovery (the largest British find this century) off the Shetlands.

Scotland should not part ways with the rest of Britain, since England is its biggest market. But Britain is planning to part ways with the EU, which is its biggest market.

There can be no independence referendum until the terms of Brexit are known, as it would be unfair on the Scots to vote without knowing the details. This is the most ironic argument of all, since the 2016 Brexit referendum was held without the conditions being known. Some people argued that Britain would still stay part of the single market, or the customs union; now it seems it will leave both. The Leave campaign argued, falsely, that Britain paid £19bn to the EU and that £350m a week could be spent on the NHS if it left. If a Scottish vote in 2018 would be unfair, then the original Brexit vote was unfair.

Of course all these arguments, rather like chess, are a matter of logic. In the real world, Mrs May can win the game by refusing to play and denying the Scots their referendum. That may succeed in the short term but in the long term, such an exercise of power seems likely to drive the union even further apart.