Joke Proof of FLT

[lhexa]

A reminder for myself:

Suppose Fermat's Last Theorem is false. Then there exist numbers x, y, and z such that x³ + y³ = z³. Because Robinson's arithmetic numerically represents all primitive recursive functions, and addition, exponentiation and equality are primitive recursive, Robinson's arithmetic proves the above equation; by first-order logic it can introduce existential quantification, and thus prove that Fermat's Last Theorem is false.

Therefore if Fermat's Last Theorem is independent of Robinson's arithmetic, Fermat's Last Theorem is true.