Premise 1: John walked .

rp ba lex John N _john NP \F.F(_john) walked S [dcl=true] \NP \Q.Q(\x._walk(x)) S [dcl=true] _walk(_john) . \X.X S [dcl=true] _walk(_john)

Conclusion: Nobody walked .

rp ba Nobody NP \P.-exists x.P(x) walked S [dcl=true] \NP \Q.Q(\x._walk(x)) S [dcl=true] -exists x._walk(x) . \X.X S [dcl=true] -exists x._walk(x)

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