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furnished. Through every phase of life, reasoning by example is a fruitful source of error in the lower order of thinkers, and hence an effective means of deception in the hands of the unprincipled.
Arguments from example may be either invented or real. An argument against the majority determining the laws which govern a city might be made by inventing the example of a majority determining the best method of performing a difficult surgical operation, rather than leaving the case to one skillful surgeon. The argument derives its force from the fact that knowledge and skill bear the same relation to the making of laws that they do to surgery. The example taken must be true to experience, else it has no convincing power. Every one knows the relation between knowledge and skill, and a successful operation in surgery. If a fictitious city had been presented as having been ruled disastrously by the majority, the example could have had no force whatever, because the example assumes the fact to be proved. The invented examples in the allegory, the fable, the parable, are used to make a general truth clear, and not as arguments to establish it.
A prominent form of argument from effect to cause is that of testimony. The fact in the mind of the witness is produced by the cause sought, and the conviction is produced through the belief that the witness will speak the truth rather than a falsehood. In such proof there can be only a probability of the fact testified to because all men do not always speak the truth. The degree of probability depends on
(1) the power, and (2) the desire of the witness to speak the truth.
1. There is a wide difference as to the value of the testimony of two witnesses equally honest. One may have powers of observation which enable him to see an object or an occurrence more distinctly, clearly, and fully than another, or superior powers of inference, that he may interpret correctly what he sees, or greater skill in expressing what he sees, that others may receive the correct impression of the matter under question. Two persons seldom see and report things exactly alike, however much they may desire to be true. The impression made on the mind by the senses are the same; the divergence begins with the facts observed. Hence, in cases of proof by testimony, the witness is confined to a statement of what the senses report. But this is only a question of degree, for unconscious inferences are a part of almost every act of sense perception. When the witness reports that he heard a certain object or that he saw an object of a given form, size, and at a given distance, he reports more than the senses give. In all the acquired sense-perceptions, that which is literally given by the senses and that given by the judgment cannot be separated, except by a conscious process of analysis. The conscious element is the act of sense-perception, and not the act of inference. Therefore, statements of the truth gained by acquired sense-perceptions are taken in testimony as matters of fact rather than as matters of inference or of opinion. The one shades off into the other so gradually that no definite boundary can be fixed.
Therefore, it would seem that too much emphasis is often placed on the difference between statements of facts and statements of opinion. Practically, a matter of fact must be limited to an individual concrete object, while a matter of opinion consists of a general truth.
2. The convincing power of a witness not only depends on his power to comprehend the truth accurately and fully, and to state it clearly, but also upon his desire to state the truth, the whole truth, and nothing but the truth. Even when the witness has no special prejudice in the case under trial, his narrow-mindedness, his general prejudices, his confirmed habit of taking partial views of questions, seriously invalidate his testimony. If the witness has some personal interest involved in the trial, it is expected, in the weakness of human nature, that he will consciously or unconsciously color the facts and opinions to accord with his own interests. But if the witness testifies against his own interest, the testimony has greater value than if he were without bias; for in so doing he proves his adherence to truth. Thus it is when a candidate for office testifies to the high character of his opponent; a man in business recommends the methods of his competitor; one who disbelieves in evolution assents to facts and conclusions which tend to support that theory; or one friend bears witness against another in favor of a common enemy.
The value of a witness depends on his knowledge and veracity, as explained in the foregoing. If his character is sufficiently high, a single witness will establish the truth under question. Other things equal, the greater the number of witnesses, the more effective is the testimony produced; but one competent witness, as a physician testifying to some point of practice in medicine, would carry conviction against any number of illiterate and non-professional men. One able and honorable statesman is more competent to bear witness on the value of a measure for general good than the mass of voters who may be called upon to testify at the ballot. Whatever the character, the number of witnesses has great force when, without the opportunity for collusion, they bear concurrent testimony. In this case their agreement could not be accounted for on any other ground than the truth of what they say.
Authority is a kind of effect from which valuable arguments may be produced. It differs from testimony in that testimony respects a matter of fact, while authority, a matter of opinion. In authority we accept the conclusions others have reached after an investigation of the question at issue. This is often the most forcible proof that can be produced, for the conclusions may be of an expert, or many such, involving a wider investigation of facts than would be possible for the immediate occasion. In law, opinions delivered by courts of justice are taken as unquestioned proof in cases which the opinion covers.
GENERAL LAWS OF ARGUMENTATION. The Law of Purpose. — The practical value of an argument is not measured by its absolute logic, but by the progress from one mental condition to another, made in the mind of those addressed. Such progress may require the closest logical articulation of the subject-matter; as, when the purpose is to present the logic of the subject for its own sake. In this case those addressed are supposed to be seeking the reason involved in the question for the sake of that reason. The mind desires the whys and the wherefores of things, and it appeals to argumentation to gratify this desire. In this case the argument has no end beyond the logic of the argument itself; hence, the logical continuity in the argument measures the progress desired in the mind addressed. The arguments in geometry are of this class. It is possible to argue questions of free trade and protective tariff in the same spirit; that is, not as an advocate who has an ulterior end, but as one investigating truth for truth's sake. In such cases the mind addressed is supposed to be in search of the truth, and needs no rhetorical device to stimulate it to active appropriation. Such arguments are supposed to fall outside the subject of rhetoric into that of logic; yet the strictest logical argument must form the basis of adaptation to minds in other conditions than that above described; just as the logical arrangement of subject-matter in description, narration, and exposition forms the basis of adaptation to the various conditions and changes to be produced by those processes of discourse.