:: deftheorem Def41 defines P#4 FOMODEL4:def 41 :
for S being Language
for b₂ being Relation of (bool (S -sequents)),(S -sequents) holds
( b₂ = P#4 S iff for Seqts being Element of bool (S -sequents)
for seqt being Element of S -sequents holds
( [Seqts,seqt] in b₂ iff seqt Rule4 Seqts ) );