Sophistic & Logic

This stratagem relies on the logical rules of induction. An induction argument is hard to make and easy to destroy.

Original text

This is a case of the diversion by means of an instance to the contrary. With an induction (epagoge), a great number of particular instances are required in order to establish it as a universal proposition; but with the diversion (apagoge) 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, eustasis. 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.