THE Oxford Dictionary’s word of the year 2016 is “post-truth”, meaning a culture in which objective facts are less influential in shaping opinion than emotional appeals. It was chosen ahead of rival buzzwords “Brexiteer” and “alt-right” which, as it happens, are rather good examples of post-truth.

The Brexiters of Vote Leave claimed £350 million a week would be repatriated if Britain left the EU, which could be used to finance the NHS. Everyone knew the claim, emblazoned on Boris Johnson’s red battle bus, was untrue.

The Institute for Fiscal Studies among others insisted it was plain wrong. But Brexiters persevered with the post-truth claim as it sort of felt right. It gave people with animosity towards the EU a thin financial justification for leaving.

Similarly, the “alt-right”, the ultra-right-wing shock-jocks who populate American social media, were shovelling loads of post-truth into the US presidential campaign: tales about the Pope supporting Donald Trump and Hillary Clinton being investigated for murder. Some of the alt-right untruths found their way into Donald Trump’s early campaign, including the claim that Barack Obama was not an American citizen (“birtherism” and that he had founded Islamic State.

The alt-right revels in post-truthism. Stephen Bannon, boss of the right-wing website Breitbart (“chief strategist” to the president-elect) doesn’t worry too much when one of his reporter’s stories is confirmed as fantasy. “Honey badger don’t give a sh@t” he reportedly declares, alluding to an obscure viral meme. He means: “We’re above the normal standards of truth because we know that, even if the facts are wrong, we’re telling a higher truth”.

Post-truth isn’t new. Tabloids such as The Sun ran stories like Freddy Star Ate My Hamster knowing they weren’t true. Even the former editor of Private Eye, Richard Ingrams, was wont to say, when he was offered a story that didn’t stand up to scrutiny, that it “had the ring of truth”. That nearly bankrupted the magazine as it staggered under the weight of libel actions. His successor, Ian Hislop, turned to more conventional standards of veracity.

This underlines one important point about post-truth politics:, that it relies a great deal on social media for impact. Since Facebook, Twitter and so on don’t abide by the standards of authenticity and accuracy that govern (most) of the print press, nonsense can spread as fast as a mouse click.

People only half believe what they see on social media anyway. It has become a post-truth nether world in which readers willingly participate in their own deception because it feels good. Politicians are supposed to be better than this and the point of elections is to put a programme to the voters you intend to honour when in office. But no sooner had Mr Trump prevailed last week than his minions began to build down his manifesto.

The 1,000-mile “beautiful wall” he said he would build at the Mexican border to keep out illegal immigrants has been reduced, at least in part, to a fence. The 11 million illegal migrants he suggested he would deport became three million, then two million “criminal elements”. This will no doubt wither further as the cost of deporting so many illegals becomes apparent. Mr Trump has also cast doubt on his threat to leave Nato to its own devices; talked about keeping large parts of Obamacare; and kept quiet about imprisoning Hillary Clinton. His followers don’t seem to be too bothered; it’s almost as if they don’t expect him to honour his promises.

It has been said that the media took Mr Trump literally but not seriously, whereas his voters took him seriously but not literally. It is as if they were in on the joke: that, of course, they knew you can’t go around deporting millions of Latinos and building crazy walls. But the very ambition marked Mr Trump out as someone they could relate to. These things that are said in bar-rooms where late-night male (and female) bonding sessions often involve condemnation of radical feminists, transgender groups and illegal immigrants.

They know they can’t do much about minority rights but, by echoing fantasy retribution, Mr Trump shows he is a regular guy.

Feeling is a large part of post-truth politics but I think there is another facet to it that derives from the general retreat from intellectual certainty. On any university humanities course, students are likely to be taught that there’s no such thing as “the facts”, only points of view that assemble partial truths.

This started with critical theory, structuralism and Karl Marx’s dictum that “the ruling ideas of any age are the ideas of the ruling class”. This is broadly true, though it shouldn’t be taken to mean that classes live in different universes.

This intellectual relativism has percolated through American campuses, riven with culture wars and gender and race studies. It has bred a profound, and often justified, suspicion of establishment figures who rest their arguments on “the facts”.

The claim, often heard in 2016, that people no longer believe in “experts” is a popular version of this relativism. However, taken to extremes, this kind of post-truth politics undermines confidence in objective truth itself.

Facts are endlessly malleable and subject to wildly speculative interpretations. In the age of spin in the mid to late 1990s, spin doctors often talked about recycling “porky pies”, those not-quite lies that were regarded as harmless and fair game in political debate. Gordon Brown used spin to confuse voters about government spending plans.

Since democracy began, politicians have always made claims that they cannot honour. The SNP famously said it would cancel all student debt and abolish the “unjust” council tax but quietly dropped these and other pledges in office.

The difference here, perhaps, is that Mr Brown didn’t actually lie about how much he was going to spend on public services after 1997; he just added the figures together in a misleading way. Similarly, the SNP did at least abolish university tuition fees and had intended to introduce a local income tax but couldn’t get a majority for that means of replacing council tax. These were, as it were, honourable untruths.

What we are seeing is the conscious projection of untruth, a kind of mutual deception in which voters connive in their own misinformation. The claim that cabals of Jewish bankers were responsible for the financial crash, for example, is now commonplace on the web.

It happens that some bankers are Jewish but that doesn’t mean they are part of a conspiracy. As with the infamous Protocols of the Elders of Zion, some people want to believe these anti-Semitic lies.

Until social media is required to observe elementary standards of honesty, fairness and accuracy we are going to see a lot more like that. Like it or not, post-truth politics is here to stay.