now :: thesis: for Seqts1, Seqts2 being Subset of (S -sequents) st Seqts1 c= Seqts2 holds
(R#3b S) . Seqts1 c= (R#3b S) . Seqts2

let Seqts1, Seqts2 be Subset of (S -sequents); :: thesis: ( Seqts1 c= Seqts2 implies (R#3b S) . Seqts1 c= (R#3b S) . Seqts2 )
set X = Seqts1;
set Y = Seqts2;
assume Seqts1 c= Seqts2 ; :: thesis: (R#3b S) . Seqts1 c= (R#3b S) . Seqts2
set R = R#3b S;
set Q = S -sequents ;

now :: thesis: for x being object st x in (R#3b S) . Seqts1 holds
x in (R#3b S) . Seqts2

let x be object ; :: thesis: ( x in (R#3b S) . Seqts1 implies x in (R#3b S) . Seqts2 )
assume A1: x in (R#3b S) . Seqts1 ; :: thesis: x in (R#3b S) . Seqts2
reconsider seqt = x as Element of S -sequents by A1;
[Seqts1,seqt] in P#3b S by A1, Lm30;
then seqt Rule3b Seqts1 by Def38;
then ex t1, t2 being termal string of S st
( seqt `1 = {((<*(TheEqSymbOf S)*> ^ t1) ^ t2)} & seqt `2 = (<*(TheEqSymbOf S)*> ^ t2) ^ t1 ) ;
then seqt Rule3b Seqts2 ;
then [Seqts2,seqt] in P#3b S by Def38;
hence x in (R#3b S) . Seqts2 by Lm27; :: thesis: verum

end;

hence (R#3b S) . Seqts1 c= (R#3b S) . Seqts2 ; :: thesis: verum

end;

hence for b₁ being Rule of S st b₁ = R#3b S holds
b₁ is isotone ; :: thesis: verum