reserve T for non empty RelStr,
  A,B for Subset of T,
  x,x2,y,z for Element of T;

theorem
  T is filled implies for n being Nat holds Finf(A,n) c= Finf
  (A,n+1)
proof
  assume
A1: T is filled;
  let n be Nat;
   reconsider n as Element of NAT by ORDINAL1:def 12;
  ((Finf A).n)^f = Finf(A,n+1) by Def6;
  hence thesis by A1,Th1;
end;
