Def P  Q == Q  P

is mentioned by

Thm* r1:(T1T1Prop), r2:(T2T2Prop). Thm* T1 = T2 Thm*  Thm* (x,y:T1. r1(x,y)  r2(x,y)) Thm*  Thm* WellFnd{i}(T1;x,y.r1(x,y))  WellFnd{i}(T2;x,y.r2(x,y))

[wellfounded_functionality_wrt_implies]

In prior sections: core

Try larger context: StandardLIB IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html