This is a case of the _diversion_ by means of an _instance to the
contrary_. With an induction ([Greek: epagogae]), a great number
of particular instances are required in order to establish it as a
universal proposition; but with the _diversion_ ([Greek: apagogae]) a
single instance, to which the proposition does not apply, is all that
is necessary to overthrow it. This is a controversial method known
as the _instance_--_instantia_, [Greek: enstasis]. For example, "all
ruminants are horned" is a proposition which may be upset by the
single instance of the camel. The _instance_ is a case in which a
universal truth is sought to be applied, and something is inserted in
the fundamental definition of it which is not universally true, and by
which it is upset. But there is room for mistake; and when this trick
is employed by your opponent, you must observe (1) whether the example
which he gives is really true; for there are problems of which the
only true solution is that the case in point is not true--for example,
many miracles, ghost stories, and so on; and (2) whether it really
comes under the conception of the truth thus stated; for it may only
appear to do so, and the matter is one to be settled by precise
distinctions; and (3) whether it is really inconsistent with this
conception; for this again may be only an apparent inconsistency.