enthymemes by which arguments are refuted of a different kind from those by
which they are established; for it is clear that demonstration or bringing an
objection is the means of refutation. By the first the contrary of the
adversary's conclusion is demonstrated; for instance, if he has shown that a
thing has happened, his opponent shows that it has not; if he has shown that a
thing has not happened, he shows that it has. This, therefore, will not be the
difference between them; for both employ the same arguments; they bring forward
enthymemes to show that the thing is or that it is not.