reserve fi,psi for Ordinal-Sequence,
  A,A1,B,C,D for Ordinal,
  X,Y for set,
  x,y for object;

theorem
  inf A = {}
proof
A1: inf A = meet A by ORDINAL2:8;
  then A <> {} implies thesis by Th8,SETFAM_1:4;
  hence thesis by A1,SETFAM_1:def 1;
end;
