A very short dialogue-story, where the Tortoise teaches Achilles that in the strictest sense of Logic, the process of inference from even 2 propositions to an almost automatically-implied third proposition involves an infinity of intermediate propositions, making it an infinite schema. The logic of that Logic is infuriating and an objection hard to nail down :-). To illustrate this, the Tortoise uses the statements of the First Proposition of Euclid and befuddles Achilles over the next couple of pages. In the end, Achilles proposes that the Tortoise be renamed, “Taught-Us”, and in response, the Tortoise proposes the other be called, “A Kill-ease”...
I am not really certain this is "mathematical fiction". It is more of a Socratic dialogue more than it is a story with a plot and characters, and it is more about philosophy than math. However, I agreed to include it at Vijay Fafat's request.
Original publication information: Mind, Volume IV, Issue 14, 1 April 1895.