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. XXVI. A brilliant move is the _retorsio argumenti_, or turning of the tables, by which your opponent's argument is turned against himself. He declares, for instance, "So-and-so is a child, you must make allowance for him." You retort, "Just because he is a child, I must correct him; otherwise he will persist in his bad habits." XXVII. Should your opponent surprise you by becoming particularly angry at an argument, you must urge it with all the more zeal; not only because it is a good thing to make him angry, but because it may be presumed that you have here put your finger on the weak side of his case, and that just here he is more open to attack than even for the moment you perceive. XXVIII. This is chiefly practicable in a dispute between scholars in the presence of the unlearned. If you have no argument _ad rem_, and none either _ad hominem_, you can make one _ad auditores_; that is to say, you can start some invalid objection, which, however, only an expert sees to be invalid. Now your opponent is an expert, but those who form your audience are not, and accordingly in their eyes he is defeated; particularly if the objection which you make places him in any ridiculous light. People are ready to laugh, and you have the laughers on your side. To show that your objection is an idle one, would require a long explanation on the part of your opponent, and a reference to the principles of the branch of knowledge in question, or to the elements of the matter which you are discussing; and people are not disposed to listen to it.