Are always a good thing, but for some, they are so open that what common sense they've got falls out through the hole. :-)

I deliberately didn't sign off "There are some things Man was never meant to know", since I don't believe in NOT pushing the boundaries. However, it will take a radically new tack to literally "think outside the box" of Space-Time.

It will take a new Einstein who will appear crazy to many and inspired to a few, and it will take a lot of work to confirm the ideas.

Of course, we can SPECULATE about multiple Universes; whether parallel, unequal, chaotic, layered, sequential or whatever. In a deterministic sense, perhaps only one of these is possible. In a Quantum sense, perhaps all are simultaneously possible, until we look and find Schroedinger's cat grinning back at us from a single solution of an infinitely indeterminate problem! (or is that just the grin of the Cheshire Cat, smiling back from beyond space-time)?

It's more Philosophy than Science.

BTW, the Flatlander example was derived from prior work, but I read the piece back in high school and have no idea who originally wrote it, but it was one of the "masters". The analogue is so deeply embedded in modern physics teaching that I can't find a direct reference to the original.