I have two favorite stories. This in itself unremarkable fact would have remained hanging around in the back of my mind if I had not accidentally re-read one story first, then remembered the second, then thought about how similar they are and why this happened, etc. These stories - “Tlön, Ukbar, Orbis Tertius” by Borges and “Ultima Thule” by Nabokov - talk about many different things, but in many ways about the same thing.