. . . which you think plausible but probably unprovable? And I don’t mean “there’s a sock eating monster hiding behind my dryer, tee hee!” but things where you think there really could be something to it – but doubt much evidence will ever come to light, alas.
Two of mine:
First, many societies exhibit a very long term cycle, on the order of ~75-85 years or so, where one generation lives through an all-encompassing existential crisis or transformation whose memory serves as a warning for the next two generations or so, until that era passes out of living memory for the most part and a similarly urgent crisis comes along. For the US it was the American Revolution, the Civil War, then World War II, and we’re due for another one very soon. Perhaps for some societies it’s a longer or more variable cycle, e.g. with England/the UK and the Civil War, the Seven Years War, the Napoleonic Wars and World War I.
Second, and more outlandish, I think there may be phenomena in the world that humans not only cannot explain, but cannot even “see” properly because it involves intrusions some other sphere of existence we’re not equipped to perceive. People in ancient China might have seen dragons flying through the sky, while ancient Israelites saw a miraculous wheel, medieval peasants saw demons and people in our society see spacecraft, and they’ve all been equally right and all been equally wrong. If you yourself were standing and looking at one of these things in our time, your mind really would fill it in with rocket fins and portholes and whatnot because you’re simply not equipped to perceive what’s really there.
Go ahead and rip the above the shreds, I’ll just shrug. As I say, I don’t expect any of this ever to be supported by any evidence, but I can’t help suspecting it’s true nonetheless. The point, though, is: what are your own private unfounded theories?