"Axiomatic" is a science-fiction short story by Australian writer Greg Egan,^[1] first published in Interzone 41 in November 1990.^[2] The short story was included in the collection The Best of Greg Egan in 2020.^[3]

A man introducing himself as Mark Carver, illegally buys a certain kind of implant known as axiomatic. Just like the axioms in arithmetic, which are postulates creating a mathematical system, which not be questioned by that system, an axiomatic can alter a belief in the brain, for example to change religion or sexuality. This doesn't contradict free will as an axiomatic can be added or removed by choice and people can freely chose how to live with their new belief. Mark Carver uses the axiomatic to block his moral and ethic beliefs concerning murder for three days and uses them to shoot Anderson, the murderer of his late wife Amy. While doing so, he is overwhelmed by the pure certainty having replaced all his conflicting emotions, and later seeks to gain it again by using another axiomatic to convince himself, that the death of Amy and Anderson were totally meaningless.

The production of a short film inspired by the short story commenced in 2015,^[10] and the film was released online in October 2017.^[11]