Politically inconvenient reality is discarded by a president who claims gut instinct is more credible than hard fact

The Donald Trump administration is increasingly developing into a post-truth presidency and the costs are becoming clearer. On the Friday after Thanksgiving, one of the most low-key days on the US political calendar, the administration quietly released a bombshell scientific report.

Thirteen federal agencies collaborated on the major, 1,656-page study, which outlines the grave consequences of uncontrolled climate change. It predicts a devastating toll on the US economy, infrastructure, living spaces and public health if present practices continue.

The findings are alarming and unassailable. But they are also totally incompatible with the campaign of deregulation that has characterised the Trump administration’s environmental approach.

As president, Mr Trump employs a small army of scientists and experts, who have just collectively told him what they think.

His response has been to try to bury the report by releasing it during a public holiday, then scorning its findings by shrugging and saying: “I don’t believe it.”

It’s easy to see why Mr Trump prefers not to. Opposition to environmental regulation has been a cornerstone of his political profile, including dismissing climate change as a Chinese hoax designed to fleece Americans.

This is typical. The dismissal of fact and opposition to the very notion of truth as a measurable, verifiable phenomenon is essential to his presidency and, above all, to his campaign of de-institutionalisation in the US.

Mr Trump began as a national political figure by promoting an enormous and racist lie. Championing the conspiracy theory known as “birtherism”, he suggested Barack Obama was not born in the US and was therefore an illegitimate president.

Now he is president, Mr Trump frequently dismisses what his own experts say, deriding them as part of a corrupt “deep state” apparatus, full of partisan hacks. It’s the same charge he has been levelling at judges, the FBI, police and parts of the military.

Mr Trump’s political base has demonstrated an impressive appetite for falsehoods, which he is now estimated to have uttered 6,420 times in a mere 649 days as president. It’s mind-boggling.

He lies about things little and big, significant and insignificant. He lies constantly and apparently compulsively. No major American leader has ever wallowed in so much – often pointless – deceit.

People know this by now but a substantial group of Americans do not care. They believe that, through his false statements, Mr Trump is expressing a deeper or higher truth that resonates on an emotional register and therefore goes beyond mere fact.

The facts might be wrong, when, for example, Mr Trump asserts a correlation between immigration and crime. Indeed, there is a negative one: immigrants of all kinds commit crimes less frequently than native-born Americans.

But given a widespread racial and cultural hostility towards immigrants, who are often perceived as threatening the social, economic and political primacy of white Americans, the essential argument of a deadly threat is perceived as somehow correct, nonetheless.

Such “higher truths” were also embedded in administration efforts to falsely link terrorism to immigration that deliberately removed all instances of domestic terrorism from the statistical equation.

When defending Mr Trump, former House speaker Newt Gingrich asserted that violent crime is rising in US cities but was confronted with the fact that it has been consistently decreasing.

His reply perfectly encapsulated the post-truth logic. He insisted because “the average American does not think crime is down” that the two claims were “equally true”. He added: “I’ll go with how people feel and I’ll let you go with the theoreticians.”

This quintessentially Trump-style manoeuvre privileges popular prejudices over quantifiable evidence.

This attitude informed the Trump administration’s notorious championing of “alternative facts” and insistence that “truth isn’t truth” and “what you’re seeing and what you’re reading is not what’s happening.”

Politically inconvenient reality is dismissed as “fake news” and Mr Trump, with a straight face, asserts that his “gut” is more accurate than experts’ brains.

This post-truth political ecosystem is, crucially, impervious to contradiction or correction, precisely because it doesn’t purport to value or prioritise fact. Instead, the instincts of leaders and the prejudices of their followers are paramount measures of “truth”.

Since Mr Trump’s political career began with the birtherism delusion, it is unsurprising that what is now developing is an entire political atmosphere structured around the false logic of an obsessive conspiracy theory: if it feels right, it must be true.

Mr Trump’s thorough de-institutionalisation doesn’t only target existing organisations. It also attacks entire categories of knowledge.

Just as the media, police, courts, Congress and all other independent sources of information and authority must be systematically discredited and disempowered, the opponents of de-institutionalising leaders must also be denied a recourse to the facts. Otherwise, there’s every danger they might prove their point.

But if what people believe and leaders feel has primacy over verifiable or quantifiable knowledge, then meaningful conversation and, soon, political opposition, essentially ceases.

Another major obstacle to the leader’s will is swept aside − and democracy will surely die as a result.