Generalizations about the tastes and interests of the age are so easy that all except the most wary fall into them, and the world is full of off-hand opinions touching the condition of society and the state of the world, which are far more conspicuous for courage than for discretion. There are very few men or women in any particular period who know it intimately enough, and with sufficient insight and sympathy, to pass judgment upon it. One hears almost every day sweeping judgments about Americans, English, French, Germans, Chinese, and Japanese which are entirely valueless, unless they are based on a very broad and intimate knowledge of these various peoples, a knowledge which, in the nature of things, few people possess. The charming American girl who declared that, since gloves are cheaper in Paris, American civilization is a failure, may stand for a type of interesting and piquant oracles, to be heard with attention, but under no circumstances to be followed. Americans are so familiar with the European traveler who arrives and makes up his opinion over night in regard to men, morals, and manners in the Western world and have so often been the victim of this self-confident critic, that they ought not to repeat the same blunder in dealing with other peoples. [Footnote: The Outlook, July 20, 1907.]
In the court room, where witnesses are present and can be carefully examined by the lawyers on both sides, it is customary to apply both mental and physical tests. The witness who testifies to knowledge of some event that occurred a long time before is given a memory test; the senses, also, through which occurrences are perceived are frequently examined. But as writers and debaters in general seldom have the opportunity to apply tests of this sort to their sources of information, and as these tests are seldom important outside of the law courts, they are not taken up in detail in this book.
The second test of the source of evidence should be:—
(2) Is the witness willing to give an accurate account of the matter?
One important influence that may cause a witness to give false evidence is self-interest. Not only individuals, but social and industrial organizations, political parties, communities, and states are frequently swayed by this emotion to the extent of deliberately perverting the truth. The evidence found in newspapers and other publications is often false, or at least misleading, because it has been tampered with by those who put their selfish interests before all else. The owner of an industry protected by a high tariff would scarcely be considered a reliable witness in matters affecting tariff reform. The opinion of a railroad magnate on the subject of a compulsory two-cent rate law would not be considered as unbiased. No disinterested seeker after truth would accept the political conclusions of a newspaper owned by a politician or recognized as the organ of a certain party. In all such cases, self-interest may prompt the witness to make statements not in strict accordance with the truth. Perjury in the court room is not uncommon; falsehood elsewhere must be guarded against. The arguer should always carefully scrutinize the testimony of a witness that has any special interest in the matter for which evidence is being sought. Though the self-interest is strong, the witness may be willing to state the matter accurately; but, as long as human nature remains as it is, this willingness should not be taken for granted.
The third test of the source of evidence should be:—
(3) Is the witness prejudiced?
Another emotion that frequently keeps a witness from telling the exact truth is prejudice. Every one is familiar with instances of how this passion warps men's morals and corrupts their judgment. If a man is prejudiced for or against a person or a system, he cannot be accepted as a trustworthy witness in matters where his prejudice comes into play. Should an economist known to favor socialism write a treatise advocating municipal ownership of public utilities, his evidence and his reasoning would not be convincing; it would be taken for granted that he looked at the subject through socialistic spectacles. A person who sets out with the expectation and intention of finding flaws in anything usually succeeds. Though he is willing to tell the exact truth, yet because of his prejudice he is sure to see only that which will coincide with his preconceived opinions. For this reason, political speeches and intensely partisan books and papers are invariably unreliable sources of evidence even though they are not intentionally dishonest.
The fourth test of the source of evidence is:—
(4) Does the witness have a good reputation for honesty and accuracy?