Science fiction assumes the universe is impersonal and knowable. Fantasy assumes the universe is governed by gods and other supernatural entities and is fundamentally unknowable by humans.

Horror is like fantasy but it also assumes the supernatural entities are cruel.

I’m pretty sure Joe Haldeman gets credit for these distinctions. He noted that by these definitions, the genre closest to science fiction isn’t fantasy — it’s the procedural mystery.

This was more of a big deal in the 20th Century, but even then, the best writers shrugged it off and were happy to play across genres. Poul Anderson said the biggest fantasy is that our understanding of the laws of the universe would be valid in 1,000 years.

I love Star Trek but the science and technology of Trek is less plausible than Game of Thrones. The science and technology of Doctor Who is even more implausible than Trek, but I love Who too.

I prefer science fiction to fantasy but I don’t make a Thing about it, like Some People do (or did — I think perhaps this controversy died in the 90s, and good riddance to it). I literally have friends who are fantasy writers.

From an excellent Bluesky threadlaunched by John Scalzi.