I liked the idea that, in order for you to study magic, there would have to be some kind of significant price paid, that magic wouldn’t be something you would happen to be born to, or understand intuitively. Thus, the magician who was going to instruct you would be not so much a donor as a vendor.

Could any of us resist using [the Device] in some manner? I would probably pop across to an adjacent Earth so I could visit my parents and grandparents, or maybe buy Alfred Bester a drink. … Or would I become obsessed with using it to avert some disaster or personal pitfall? Even if it were nearly impossible to alter events on most Earths, it would be a wondrous tool for historians and scientists, but might be a very dangerous technology for any government to possess.

The tokens are just one of the million weird little details I don’t even try to explain—the story is full of “exposition around the edges,” little throwaway things that imply a vaster universe where the story takes place. In my mind the tokens are sort of like the coins that people used to put on the eyes of the dead to pay the ferryman to take you into the afterlife—some kind of magical token to aid your journey to the land of the dead, a last kindness that a colleague can bestow upon you.

The difficulty was in trying to make the time and place more real—all this happened more than a thousand years ago, and in a part of the world that we don’t usually learn much about. Set a story in Ancient Rome or 12th Century England, and the reader will most likely have a mental file of background information; medieval Kiev is pretty much a mystery.

The notion of basilisk images was something I’d had in mind ever since reading Douglas Hofstadter’s Gödel, Escher, Bach. Hofstadter’s favourite analogy for the impact of Gödel’s Theorem on mathematics is a music recording that can’t be played because its resonances destroy the playing mechanism.

I obediently spent my childhood writing little stories, until I reached that age when you dig in your heels and tell your parents you hate them and you’ll never, ever be what they want you to be. And I more or less ran away with the circus for the next twenty years.

A couple years ago when I was actively blogging, some editorial minion had complained about their slushpile being full of stories with titles that spoiled the ending mixed with time-travel stories about people trying to kill Hitler. I commented that maybe it wasn’t a good time to submit my story titled “The Cross-Time Accountants Fail to Kill Hitler Because Chuck Berry Does the Twist.”

I really wanted to write about this world I’d discovered, its rich, slow secrecy—its winter melancholy that turned gradually, then all at once, into an astoundingly fecund summer. To do that, I needed a plausible way for Molly to stay behind, to live reasonably well in an otherwise-abandoned version of the place. I hit upon a creeping apocalypse.

If you’re looking at society at large, I think there would be a lot of civil unrest inspired by the destruction of our society’s existing certainties about the way the world works. I imagine millennial cults would develop and that traditional religious belief would see a sharp rise. Secular and scientific voices would likely be drowned out.