Typed First-order Logic (TFF)

New logic features

Problem

In logic

In TPTP format

Challenge problem

Geoff is the only teacher of Joe (hint - functions have only one result). Joe is not stupid but Joe failed. If a student failed then either the student is stupid or there is is some other student with the same teacher who also failed. Therefore there is some student other than Joe, also taught by Geoff, who also failed.

Non-theorems