 To the rejoinder that rationality and irrationality are not actually present in the same thing, Abelard offers a twofold reply. First, he rejects the claim that they are present only potentially. Each species is actually informed by a contrary, and the genus is actually present in each as a whole; hence it is actually informed by one contrary in one species and by the other in the other; since it is wholly one and the same in each, it is therefore actually informed by contraries, and the contradiction results. Second, Abelard undertakes to establish that contraries will be present not merely in the genus but even in the selfsame individual. For Socrates is (an) animal, and so is Brunellus the Ass; but by transitivity—since each is wholly and completely animal—Socrates is Brunellus, and hence both rational and irrational. Put a different way, each is essentially an animal, and furthermore essentially rational and essentially irrational.