theorem Th22:
  Ant(f) |= p '&' q implies Ant(f) |= q
proof
  assume
A1: Ant(f) |= p '&' q;
  let A,J,v;
  assume J,v |= Ant(f);
  then J,v |= p '&' q by A1;
  hence thesis by VALUAT_1:18;
end;
