theorem
  {p} is Filter of L implies L is upper-bounded
proof
  assume {p} is Filter of L;
  then reconsider F = {p} as Filter of L;
  take p;
  let q;
  p in F by TARSKI:def 1;
  then p"\/"q in F by Th10;
  hence thesis by TARSKI:def 1;
end;
