
theorem
  for H being non empty RelStr st H is Heyting for b being Element of H
  holds b = (Top H) => b
proof
  let H be non empty RelStr;
  assume
A1: H is Heyting;
  let b be Element of H;
  (Top H) => b <= (Top H) => b by A1,ORDERS_2:1;
  then Top H "/\" ((Top H) => b) <= b by A1,Th67;
  then
A2: (Top H) => b <= b by A1,Th4;
  (Top H) => b >= b by A1,Th72;
  hence thesis by A1,A2,ORDERS_2:2;
end;
