The fundamental theorem of software engineering (FTSE) is a term originated by Andrew Koenig to describe a remark by Butler Lampson:[1]
"We can solve any problem by introducing an extra level of indirection."
The term is facetious, in the sense that it doesn't describe an actual theorem that can be proved, and the problems it solves are not fundamental. Rather, it's a principle for getting around the restrictions of a given programming environment.