Читать книгу The theory and practice of argumentation and debate - Victor Alvin Ketcham - Страница 56

The investigator must not stop collecting evidence until he has amassed a sufficient amount to prove his proposition. Naturally the question is at once asked, “What is the amount of evidence required to prove a proposition?” To answer this question in a satisfactory manner some careful thought is required. Since we are regarding argumentation as a practical art, and since when we consider it in this way we must conclude that its end is action, we are forced to admit that the amount of evidence is not sufficient unless it actually produces the result aimed at,—namely, the action of the person or persons addressed in a manner which conforms to the wishes of the arguer. It is therefore plain that the amount of evidence required varies with individual cases. The arguer must consider the importance of the question to those to whom the argument is addressed, as well as their prejudices and personal interests. He must consider these things in their relation to the present situation and then determine the amount of evidence in accordance with what his judgment tells him is required. If the argument is to be passed upon by judges whose duty it is to reach a conclusion but who are not personally interested in the result, the following rule may be applied: Sufficient evidence must be produced to satisfy an unprejudiced mind beyond a reasonable doubt.

In relying upon the above rule we must eliminate prejudice, personal interest, and results terminating in active or prolonged action. Therefore if prejudice or personal interest exists in any particular case, the first duty is to remove this prejudice or nullify the personal interest. If active or prolonged action is desired evidence sufficient in amount to induce this action must be produced. With these two limitations the rule stated above may be accepted as the measure of the amount of evidence required. There are, of course, some facts which may be presented without relying upon any special evidence or authority for their truth. All facts which are matters of common knowledge come within this class. Geographical facts, such as the fact that Boston, New York, and Savannah are seaports; historical facts, such as the fact that Alaska was purchased from Russia; political facts, such as the fact that the Southern States are largely adherents of the Democratic Party; and things which must have happened in the ordinary course of nature, such as the presumed death of a person born two hundred years ago, all may be stated without evidence to support them.

In determining the amount of evidence to be offered it is sometimes necessary to consider the different sources from which it is derived. Care should be taken not to place too great reliance upon one source. For example, in a debate on the prohibition question one speaker quoted statistics from a bulletin issued by the Anti-Saloon League, he relied for proof of his facts upon a committee report of the Anti-Saloon League, he offered the opinion of the President of the Anti-Saloon League, and finally quoted from the argument of a lawyer who is employed by the Anti-Saloon League. Aside from the charge of prejudice which might be made against this evidence, it is readily seen that too much reliance is placed in one authority. It might well be termed “an Anti-Saloon League argument.” No person is willing to accept some other person’s opinion or evidence in preference to his own, but if a number of authorities have arrived at substantially the same conclusion, or can offer evidence which points to the same conclusion, and there has been no collusion between them, any reasonable person will give such conclusions his most serious consideration. Furthermore, if the speaker or writer indicates that his evidence comes from various sources, it inspires confidence in his words, since the variety of the evidence offered indicates that the investigation has been broad and thorough.

The process of collecting evidence set forth in this chapter may be used in other fields besides that of argumentation. Every individual has frequent occasion to collect evidence regarding certain subjects connected with his business or occupation. Whatever the occasion for investigation the method of collecting evidence herein presented can be used to great advantage.

The student of argumentation is cautioned to follow explicitly the directions contained in this chapter. All the available sources of evidence should be consulted. The rules regarding the recording of evidence should be adhered to strictly. The recorded evidence should be carefully studied, with the view of determining its relative importance, according to the rules laid down for the selection of evidence. The student should feel satisfied in his own mind that he has secured an amount of evidence sufficient to establish each main issue. Then after these tasks are completed he can turn his attention to the next great step in argumentation,—the Construction of the Brief.

EXERCISES IN COLLECTING EVIDENCE

1. Make out a list of topics under which you would look for material on the following propositions:

a. The United States should impose a tariff for revenue only.

b. The United States should provide for an immediate increase in the navy.

c. Intercollegiate football should be abolished.

d. Children under fourteen years of age should be prohibited by law from working in factories.

e. Marriage and divorce should be controlled by Federal law.

2. What sources of evidence would you consult in regard to each of the above propositions? State one or more items (books, magazine articles, persons, or documents) under each source.

3. Write out and hand in for inspection ten cards on one of the above propositions. These cards should show the application of all the rules given for recording evidence.

4. Apply to these cards the rules to be observed in selecting evidence. Does any one of these cards or any combination of the cards show evidence sufficient in amount to prove any one contention?