There’s a concept in linguistics called an “auto-antonym” – a word that can, quite ridiculously, mean its own exact opposite. “Fast”, for example, can mean moving at speed, or unable to move at all. Or consider the sentence: “He tried to cleave them apart, but they cleaved tight to one another.”

Having words which can carry two diametrically opposed senses could, one might think, get confusing, but it rarely does: the meaning intended is almost always clear from the context (at least to a native speaker). Nonetheless, I think I’ve found a term which can carry two completely contradictory senses, in a way which many people seem not even to have noticed. What’s worse, their failure to notice this is about to take us tumbling over an economic cliff.

That term is “free trade”.

A few weeks ago, my old mate Daniel Hannan finally revealed what he’d do with himself once the EU stops paying him large amounts of European taxpayer’s money. His new “Institute for Free Trade” is a pro-Brexit think tank which will, it says, make “the moral case for open commerce”. Its name recalls that of another pro-Brexit pressure group, Patrick “lol” Minford’s Economists for Free Trade.

The funny thing about both these organisations is that they believe the case for free trade is best made by pulling Britain out of the largest and most established free trade bloc in the world. If you were truly a believer in free trade, one might think you’d want Britain to be able to trade as freely as possible with its nearest neighbour and largest trading partner. And yet, no: there’s an entire subculture of free trade fundamentalists who want us out of the single market and the customs union, effectively throwing up barriers between us and the continent.

Several explanations for this apparent contradiction come to mind, many of which you can probably guess. But one which has, I think, received relatively little discussion is that the term “free trade” is surprisingly hard to parse – it can mean, in fact, two things so distinct they’re almost antonyms.

The “free” in the free trade proposed by the fundamentalist right is a negative freedom: the freedom from regulation. The problem these guys have with the EU is (let’s be charitable) not that they’re all a bit foreign, but that it’s a bureaucratic body: it wants to interfere in the market by imposing costly regs on decent, hard-working businesses. If you think that free trade means less regulation, that should mean less EU.

But there’s another form of freedom that applies here: a positive freedom, the freedom to trade. If I want to sell my widget in your market, then the things that stop me might be government-imposed rules like tariffs; but they might also be the fact our two markets have different regulatory regimes, so that none of my potential customers know whether my widget is safe or useful or does what it’s supposed to. In the latter case, increasing the freedom to trade might mean actually increasing government regulation, by imposing common standards.

This, of course, is what the EU has done through the single market. It’s been incredibly, visibly successful, in that it’s increased trade between the members of that market. If you believe trade is A Good Thing in terms of increasing the wealth and happiness of humanity, well, you should support it.

Yet some people, who claim to believe in free trade, don’t. Why? Because it doesn’t fit their idea of freedom – because it conceives of government not as a barrier to freedom, but as the body that facilitates it.

Those people are now in the ascendant, and determined to take us out of this free trade area. They’re such keen supporters of free trade, that they’re willing to massively reduce Britain’s trade to show their support. Black is white, up is down, and words have no meaning any more.