If I were to tell you that people at the highest levels of world government - the very highest levels - had entered into a clandestine agreement to poison the global bee population, thereby preventing proper pollination of crops, collapsing international food supply and forcing starving people to rely on a chosen few multinationals (secretly owned by the aforesaid world leaders) for nourishment...you'd say to me, "Yeah? Prove it."
And I would say to you, "Prove that it isn't true."
Which of course you can't really do. There's often no evidence against a scenario that is so unlikely.
Especially one that is apparently "secret".
And even if you did come up with something that countered my belief, I could try to persuade you that it was planted because "that's what they want you to think. Come on sheeples, the truth is out there!"
And that's how you start a conspiracy theory.
The lack of evidence for your theory is all part of the set-up ("They're covering their tracks!"), making them devilishly hard to dismantle.
In fact, conspiracy theorists often start with an incontrovertible truth (the world bee population is in fact declining) then spin on that to weave their tale, pulling in various common prejudices to beguile the rest of us (fear of elites, disgust at the behaviour of multinationals, resentment at feeling manipulated by government).
While they end up with something far-fetched to most of us, to those predisposed to suspicion, they can ring true.
Which brings me to QAnon, the far-right conspiracy theory movement increasingly embraced by Trump supporters in the US.
It posits that a deep state plot against Donald Trump was headed off, at least in part, by Q, a supposed secret service agent or government official who posts on fringe websites and social media channels.
Trump was the deep state's target because he became president in order to dismantle a powerful international cabal of Satan-worshipping paedophiles, including Barack Obama, Hilary Clinton (naturally) and George Soros.
Yes, I know.
Within QAnon, Trump is a kind of saviour figure, come to rescue the US - nay, the world - from evil at its most depraved.
So all of Trump's bungles and deficiencies are just background noise - his real job is so much more important, understand? It's a licence to let him get away with pretty much anything.
So who benefits most from this conspiracy?
You don't have to be a genius to see that it's Donald J Trump. If I was a conspiracy theorist myself, I would say he started it, but I doubt he's creative enough.
It's hard not to think that he's capitalising on it though.
At a news conference on Wednesday, Trump addressed the subject of QAnon directly for the first time, in answer to a journalist's questions.
Trump insisted he hadn't heard much about the movement, "other than I understand they like me very much" and "it is gaining in popularity".
Hard to believe he hasn't heard much, given that a 2019 FBI briefing specifically named them as a domestic terrorism threat, Trump has himself re-tweeted QAnon-related accounts, and its symbol - not surprisingly, a large capital Q - is a common sight at Trump rallies. Last week, he praised a Republican from Georgia, who looks set for Congress and who has famously spouted QAnon guff.
Then, in what must have been a QAnon-supporters' dream come true, he congratulated them on being "people that love our country".
When the journalist pressed him further, spelling out a couple of the outlandish QAnon beliefs, Trump said - po-faced - "If I can help save the world from problems, I'm willing to do it."
They even think his choice of a pink tie was a coded message of support for them.
Which sounds ludicrous - but just try and prove it wasn't.