Premise 1: John walked .
Conclusion: Nobody walked .
Script piped to coq
echo "Require Export coqlib. Parameter _john : Entity. Parameter _walk : Entity -> Prop. Theorem t1: (_walk _john) -> (not (exists x, (_walk x))). Set Firstorder Depth 1. nltac. Set Firstorder Depth 6. nltac. Qed." | coqtop
echo "Require Export coqlib. Parameter _john : Entity. Parameter _walk : Entity -> Prop. Theorem t1: (_walk _john) -> (not (not (exists x, (_walk x)))). Set Firstorder Depth 1. nltac. Set Firstorder Depth 6. nltac. Qed." | coqtop