"What can be asserted without evidence can be dismissed without evidence." The late, great, author, columnist, intellectual, critic and scourge of fools and sloppy thinkers everywhere, Christopher Hitchens, coined this delicious idea, with an evil gleaming sharp edge, known as Hitchens's Razor.
Add to this Carl Sagan's neat "An extraordinary claim requires extraordinary proof," and you've got simple concepts that can be used like a laser to slice down loony belief and bullshit wherever they may lurk.
Let's try an extraordinary claim. The sun is 149.6 million kilometres from Earth. Extraordinary proof? Tens of thousands of years of careful scientific thought and test, documented, reviewed and refined until every element of the equation to find the distance, from the equipment, to the mathematics, and a million quantifiable variables, has stood up to the scrutiny of our finest minds. Every step in determining that number exists in the public domain and has withstood any and every legitimate intellectual challenge and so is accepted as a proven fact by the world's scientific community. That's pretty good proof.
Let's try another extraordinary claim. The Earth is flat.
Extraordinary proof? Um, a rapper called B.o.B. And because the Earth looks flat something something human eye.
This is a claim that can – should – be dismissed without evidence. That's it.
Now, I have to confess to rather obsessively following a few flat-earthers on Twitter and flying into a frothing rage at each new piece of stupidity, managing to amuse and upset myself at the same time. How can anyone be so willfully and blatantly idiotic?
Who cares if a few loons want to believe stupid stuff, they're not doing any harm, are they?
Oh, yes they are.
It's not just a few. Since B.o.B introduced flat earth theory to his 2.29 million twitter followers in 2016, the movement has been gaining a huge and growing following and worldwide popularity.
The cities in the background are approx. 16miles apart... where is the curve ? please explain this— B.o.B (@bobatl)
Confederacy of conspiracy
"No matter how high in elevation you are … the horizon is always eye level … sorry cadets … I didn't want to believe it either," he said.
To be a flat-earther, you also have to believe there is a worldwide conspiracy, thousands of years old, involving every pilot who ever flew or is flying, every astronaut from every country in space, every scientific academic in every university and institute, everyone involved in worldwide shipping, mining and tunnel construction, Elon Musk and everyone at SpaceX, all the world's governments, armies, navies and air forces. And, of course, the flat earther's arch-nemesis, NASA.
That's millions upon millions of people. Yet, in a Weinstein-Wikileaks world, there's not been one whistleblower, anywhere, ever. This says, to one's critical thinking, that there's no conspiracy.
Have a google, or look up #flatearth on social media. It's astounding. I've been called a "stupid globehead" by people who believe aircraft contrails – ice particles of frozen engine water vapour – are actually "chemtrails", governments crop dusting us with poisons to make us believe the earth is a globe.
And if Earth really is flat, so what? Why go to so much effort to keep it a secret? There's no reason for a conspiracy, no reasonable motivation.
Any evidence of a spherical planet, like photography, video, or any other recording, is, of course, dismissed as fake.
This renders any rational discussion impossible. All evidence we live on a planet, no matter how completely and utterly proved by the rigours of the scientific tradition that has brought us every luxury in our modern lives, is trumped by irrational belief.
I'm not going to debate the details, but we really don't live on a flat disc with ice around the edge and the sun and moon only about 5,000km away, flying about.
The power of fear
A thing too boring to discuss here, the silly Bedford Level experiment, a cornerstone of flat earth mythology, has been thoroughly discredited as bad science. That's how science works. Claims are tested and proved or disproved. Eclipses, the moon, the behaviour of shadows and ships on the horizon, the rest of the universe, plus a million other proofs, show the earth is unequivocally round. Every flat Earth claim has already been surgically skewered by science.
So why would anyone believe it?
"The whole idea of us being a speck of dust just an insignificant accident is nothing anyone would ever tell your kids – 'Hey, just wanted to let you know you're an accident so get out there and win today," says US flat earther, Jonathan Vincent.
That's why. It's to do with the human fear of not being the centre of everything, of perhaps being alone and responsible for our own destiny.
A post-truth world
Flat Earth thinking is dangerous because it's creating an intellectual and cultural environment where it's becoming more and more acceptable for the objective truth to be dismissed by subjective belief. It's moving us backwards as a species.
The truth, the only basis for ethics, morality, and the foundation our whole society is built on, is under threat like never before.
In war, the first casualty is truth. Misinformation, disinformation, propaganda and lies are the tools of the totalitarian.
If we're so purposefully stupid we begin to look away from things we know to be true, to dismiss the gifts of knowledge our forebears fought to bring us, the science that has have kept us alive, warm and filled our bellies so far, perhaps we deserve the world we want to believe in.
Just don't fall off the edge.