Hyslop says concerning valid inferences and fallacious ones: "We cannot infer _anything_ we please from any premises we please. We must conform to certain definite rules or principles. Any violation of them will be a fallacy. There are two simple rules which should not be violated: (1) _The subject-matter in the conclusion should be of the same general kind as in the premises_; (2) _the facts constituting the premises must be accepted and must not be fictitious_." A close observance of these rules will result in the detection and avoidance of the principal forms of fallacious reasoning and sophistry. SOPHISTICAL ARGUMENTS. There are a number of tricky practices resorted to by persons in argument, that are fallacious in intent and result, which we do not consider here in detail as they scarcely belong to the particular subject of this book. A brief mention, however, may be permitted in the interest of general information. Here are the principal ones:-- (1) Arguing that a proposition is correct because the opponent cannot prove the contrary. The fallacy is seen when we realize that the statement, "The moon is made of green cheese," is not proved because we cannot prove the contrary. No amount of failure to _disprove_ a proposition really _proves_ it; and no amount of failure to _prove_ a proposition really _disproves_ it. As a general rule, the burden of proof rests upon the person stating the proposition, and his opponent is not called upon to disprove it or else have it considered proved. The old cry of "You cannot _prove_ that it is _not_ so" is based upon a fallacious conception. (2) Abuse of the opponent, his party, or his cause. This is no real argument or reasoning. It is akin to proving a point by beating the opponent over the head. (3) Arguing that an opponent does not live up to his principles is no argument against the principles he advocates. A man may advocate the principle of temperance and yet drink to excess. This simply proves that he preaches better than he practices; but the truth of the principle of temperance is not affected in any way thereby. The proof of this is that he may change his practices; and it cannot be held that the change of his personal habits improves or changes the nature of the principle. (4) Argument of authority is not based on logic. Authority is valuable when really worthy, and merely as corroboration or adding weight; but it is not logical argument. The _reasons_ of the authority alone constitute a real argument. The abuse of this form of argument is shown, in the above reference to "begging the question," in the quotation from Bulwer. (5) Appeal to prejudice or public opinion is not a valid argument, for public opinion is frequently wrong and prejudice is often unwarranted. And, at the best, they "have nothing to do with the case" from the standpoint of logic. The abuse of testimony and claimed evidence is also worthy of examination, but we cannot go into the subject here.