theorem Th25:
  for p being Element of Funcs(Valuations_in(Al,A),BOOLEAN) holds
  FOR_ALL(x,p).v = TRUE implies p.v = TRUE
proof
  let p be Element of Funcs(Valuations_in(Al,A),BOOLEAN);
  for y st x <> y holds v.y = v.y;
  hence thesis by Th3;
end;
