Trump at a rally in Omaha, Nebraska. Credit:AP Most of what this candidate offers as policy has a shelf life – sometimes it lasts just hours; more often it survives for days or weeks. And no policy issue is too big or too small to warrant a Trump self-contradiction – guns, Syrian refugees, Hillary Clinton, healthcare, abortion, tax and torture. Republican presidential candidate Donald Trump in Charleston, West Virginia. Credit:AP Guns In 2000 Trump supports a ban on assault weapons and an enforced waiting period to buy guns; in a campaign debate in March, he flips. "I don't support it any more. I do not support the ban on assault [weapons]."

The US accepting Syrian refugees In September 2015 he tells Fox News: "On a humanitarian basis with what's happening, you have to [accept them]." Eight weeks later, he tells a rally: "The refugees are going back, we can't have them." Healthcare In 2000 he writes: "We must have universal healthcare." This year he flips: "We have a series of reforms ready for implementation that follow free-market principles." Abortion

In 1999 he tells Meet the Press: "I'm very pro-choice." In February 2016 he tells Fox News: "But I'm pro-life." Weeks later he doubles down on MSNBC, saying women who have abortions should be punished; and just hours later, that women are victims and only the doctor should be punished. Tax In 1999 he tells MSNBC: "I would tax people of wealth, of great wealth, people over $US10 million, by 14.25 per cent." Earlier this year he flips: "A big tax reduction, including for the upper income." Then a few weeks later he does a reverse-flip when CNBC asks about his proposed tax cuts for billionaires: "I'm not necessarily a huge fan of that." Torture Asked during a March 3 candidate debate, if military officers would carry out his orders to kill the families of known terrorists in breach of the Geneva Conventions, Trump insists: "If I say, 'Do it,' they're going to do it." But this the next day: "I'll not order a military officer to disobey the law."

Editorialising this week on Trump's success in putting a lock on the nomination, The Economist didn't invoke the Dunning Kruger effect, but the suggestion was in the magazine's conclusions: "These beliefs lack coherence or much attachment to reality." Does Trump believe what he says? Credit:AP "They are woven together by a peculiar 21st-century mastery of political communication, with a delight in conflict and disregard for facts, which his career in reality television has honed." Michael Lynch, University of Connecticut philosophy professor and author of The Internet of Us: Knowing More and Understanding Less in the Age of Big Data, sees more evil genius than incompetence in Trump's performance. Trump doesn't do what other politicians do when their words are badly received. Some resort to a coded "I was being a prize idiot" when they wheel out a hapless spokesman who claims the boss "misspoke"; others engage in "walking back" their comments, adding more words to make what was unpalatable more acceptable, less controversial.

But Trump goes off the reservation. Yesterday the sky was blue, today it is green. And while reporters try to hold him to account, his supporters don't seem to care. Lynch writes in The New York Times: "You can derive any proposition you wish from a contradiction in a few simple steps. Yet that's precisely what makes them so useful from the point of view of political psychology – indeed, the more blatant the contradiction the better. "Walking a comment back says you are taking responsibility for what you've said. Blatant contradiction puts the responsibility back on the shoulders of the listener. If I simply deny what I earlier affirmed and act as if nothing has happened, then you are left having to decide what I really meant." Lynch's point here is that humans are prone to what he calls "confirmation bias". We intend to interpret evidence so it conforms to what we already believe. It follows too that with many of Trump's fans claiming he's not afraid to "tell it like it is", it's up to the listener to decide what "it" is in the face of a contradiction. All this, Lynch argues, goes to Trump's appeal – and that Trump finds contradiction so useful reveals an even deeper contradiction.

"Mr Trump's explicit lack of authenticity is what makes him so authentic. He is like a walking oxymoron … To some, that he contradicts himself so freely shows that he doesn't care what 'they' [the news media, liberals, women, minorities] think. "The signal this sends is one of strength: only the strong can afford not to care." The insidious root of all this, he concludes, lies in a deeper power of contradiction. Repeated often enough, political contradiction lulls some into giving up on critical thought, and the risk when that happens is they give up on truth – at which point contradiction ceases to matter. Mass appeal: Do Trump's supporters care if he contradicts himself? Credit:AP Reports on the Dunning Kruger effect generate wonderful headlines, such as "Revisiting why incompetents think they are awesome" and '"We're all confident idiots."

And here's the headline from Dunning and Kruger's original 1999 work: "Unskilled and unaware of It: how difficulties in recognising one's own incompetence lead to inflated self-assessments." But, but, but … does the supreme confidence with which Trump steps out daily mask his own incompetence? Or, does he know exactly what he's doing and is it conceivable he will be vindicated on election day? Were the latter the case, we might have to diagnose Trump as sort-of normal; and it'll be the media and the pundit classes that'll be chuffing off to talk to therapists who, depending on the profile and ego of their client, might or might not mention this thing call the Dunning Kruger effect. Follow FairfaxForeign on Twitter Follow Fairfax Foreign on Facebook