Terra Incognita
One concept that dominated fiction for many years was that of terra incognita. Meaning 'unknown land' it was anything beyond the borders. Perhaps the frisson that we felt at terra incognita was an extension of the terror our ancestors might feel at what might lay beyond the radius of light fire could project.
In the 19th century the realm of terra incognita could still just about be found on heavily populated continents, but it was creaking badly. The formerly unknown had been mapped too well for that. By the 1920s it was all but finished. HP Lovecraft's At the Mountains of Madness is set in Antarctica, still just about terra incognita. But today we can look up the locations of the novella on online maps and see there's nothing there.
Perhaps this is why so many stories moved off world or to invented worlds: terra incognita was stolen from us and there's nowhere else to look. Following The Lord of the Rings films, the capability of such imaginary fiction to tell recognisable stories in a fresh environment with new possibilities was suddenly noticed by the mainstream.
But terra incognita is more than a literary technique, it's a call to adventure. It offered a place to beyond the borders and with that stolen away, where are the borders we can push beyond? They're all imaginary where once they used to be real.
A powerfully truthful presentation of this comes from Eric Weinstein. I think terra incognita is the unkept promise of the call to adventure that he references. It's absence of meaning and that hollows us out dangerously.
For me, terra incognita is my own nature. With years of hindsight, I can see diagnosis of autism as my call to adventure. But it's an inward journey which is the journey of a hermit or monk, of someone removing themselves. Jung thought of the subconscious as where the gods went when they depopulated the cosmos. It's a realm that drives us, as the Greek gods drove us, in ways that we don't understand.
Calls to adventure that come from the external are easier to recognise because they're open and in the light. That doesn't mean they're going to be easier to go on. But perhaps they enable us to go to Oz without needing a tornado to pick up our entire house.