I'm not talking about realistic fiction, where it seems 100% of content needs to be realistic. It's a general question I'm posing here because I think responses will be interesting and illuminating. It seems to depend on genre, but even within the most speculative genres there must be some believability. Fantasy -- create non-existent creatures (unrealistic) which follow particular rules within story (realistic in context) Sci-fi -- create space aliens and technologies which do not and may never exist (unrealistic) as long as, like fantasy, you follow your own in-house rules (realistic) Magical Realism -- my only real (heh) experience with this is Murakami, whose blood is obviously laced with LSD. These stories seem to be mostly realistic then there are mythologically or culturally or randomly inserted bits of supernaturalism or nonsense to accentuate something within the realistic-ness. When I think of Sherlock Holmes, I think of somebody who lives in a realistic universe whose deductive abilities are believably realistic although, oftentimes, at least based on the modern show with the 1.5 hour episodes, the stuff he infers from people's clothing and accessories is complete bollocks. I wonder if there is some general formula for this. There probably isn't but let's entertain the dialectic for fun: Realistic <----------------------------------------------> Unrealistic All the way on the left is realistic fiction. All the way on the right there is no such thing; there are no stories where there is no gravity, everything has 50 eyes, the languages spoken are inconsistent, the buildings are made of materials that don't exist within that universe. So there must be some optimal balance. What is it?