6. Material for refutation should be preceded at the top of the card by an exact statement of the argument to be refuted.

7. The main issues or subjects to which the evidence relates should be stated at the top of the card.

8. The source from which the evidence is taken should be definitely stated at the bottom of the card.

III. Selecting evidence.

All the reliable evidence obtainable should be collected before the selection of the exact evidence which is to go into the argument is begun. If the student has confined his collecting to the sources of evidence suggested in the first section of this chapter, the presumption will be in favor of its reliability. This presumption may be strengthened and in some instances turned into certainty by a selection made in accordance with the rules which it is the object of this section to present.

It is of the utmost importance that a large amount of evidence from which to construct the brief and argument be available. It is only in this way that the strongest evidence obtainable can be brought to the support of the argument. All the evidence used must be relevant but not all the evidence that is relevant need be used. The following rules should be observed in the selection of evidence:

1. The evidence must come from the most reliable source to which it can be traced.

All the evidence collected must have back of it some reliable source, as indicated in the discussion of Sources of Authority. The more trustworthy this source the more valuable is the evidence and the greater the weight given to it. Therefore "the evidence must come from the most reliable source to which it can be traced." Every fact offered in evidence comes from some definite source. If this source cannot be found the fact should be discarded as worthless.

To illustrate, in the investigation of a subject, a fellow-student may know some fact which is a most important piece of evidence in your favor. He may tell you about this fact, but you would not think of going into the debate and quoting one of your fellow-students as authority. Therefore you will at once ask the student from what source he obtained knowledge of the fact. He may reply that he has seen it in a newspaper article. But since a newspaper is usually of little value as an authority, you cannot rely upon its statement. Therefore you inquire from what source the newspaper obtained it. By consulting the newspaper it is found that the statement is made in an editorial which comments upon an article found in the North American Review. You must then consult the number of the North American Review to which reference is made. This is fairly reliable, and anyone would feel justified in quoting it as the source of his evidence, although he would not feel justified in quoting the statement of a fellowstudent or the statement of a newspaper.

If the statement is one which is an opinion of the editor of the North American Review, or if for any other reason it cannot be traced back of this source, North American Review, volume and page, should be quoted as the source of the evidence. But suppose that the statement can be traced to its original source. To be more concrete, let us assume that the statement is to the effect that there is a surplus of over one million dollars in the United States treasury. For such a statement the North American Review is not the most reliable source. In this case the most reliable source is the Report of the Treasurer of the United States, which can be found in almost any library. When this fact is located the student should make an exact statement of the amount of the surplus and refer to the Report of the United States Treas

urer.

Thus the fact to be used is traced through the statement

of a fellow-student, through the editorial in the newspaper, through the article in the North American Review, back to its original and trustworthy source the Report of the Treasurer of the United States. In this manner every fact presented must be traced to its most trustworthy source. In quoting the opinions of individuals the same principle should be applied. The greater the learning, ability, and reputation of the person quoted, the greater is the weight attached to his opinions.

In almost every branch of human endeavor and in every field of knowledge there are a few men who possess especial ability. By common consensus of opinion these men are regarded as authorities and their statements of fact or judgment are accepted as the most trustworthy. For example, the statements of Ely, Seligman, and Seager in the field of economics, and the statements of J. P. Morgan, and Andrew Carnegie in the field of industry and finance, are regarded as good authority. In chemistry the statements of Dr. Ira Remsen would be considered good, while in regard to psychology one could do no better than to quote the opinions of Hugo Münsterberg. Regarding the wireless telegraph, Marconi would be the most reliable source, while in the field of aërial navigation the opinion of the Wright brothers could be quoted as the most reliable. Instances of reputable sources of evidence could be cited sufficient in number to cover many pages, but the few here suggested will serve to illustrate the class of authority to which all points of evidence should be traced.

2. A person quoted as authority must be unprejudiced, in full possession of the facts, and capable of giving expert testimony on the point at issue.

In the preceding section reliable sources of evidence have been indicated in a general way. It is, however, by no means

possible in the treatment of all subjects to cite authorities so universally accepted. The opinions of persons who are not known to the general public may be given weight by means of their official position, their special work or investigation in any line, or by the favorable statements of recognized authorities regarding them or their work. As previously suggested, Who's Who in America, is a storehouse of information regarding such people.

An opinion or even a statement of fact is not likely to be looked upon with favor unless it comes from an unprejudiced source. It is not so much the question of actual prejudice existing in the mind of the person quoted as it is the surrounding circumstances which would naturally tend to cause prejudice. For example, the statement of John D. Rockefeller, in regard to the beneficent effect of monopolies on trade and commerce, might be perfectly sincere, but since John D. Rockefeller has a financial interest in the maintaining of a monopoly, it would not be advisable to quote his statements in their favor. Such statements are not only easily refuted but they lack weight because they do not appear to come from an unprejudiced source. In like manner the President of the Brewers' Association would not be accepted as authority on any matter connected with the prohibition of the liquor traffic. From the very circumstance of his position he is presumed to be prejudiced against such prohibition. The person cited as authority should have no financial interest in the subject on which he is quoted. He should be in a position to be unprejudiced.

The person quoted as authority must be in full possession of all the necessary facts. Very often this knowledge of facts may be presumed from the position which the authority occupies. The Secretary of the Navy is presumed to be in full possession of all the general facts concerning his department. The captain of a battleship would be presumed to

know all the essential facts in regard to his ship. An engineer on the Panama Canal would be presumed to be in a position to know, and actually to know, facts connected with the duties of his position. The authority quoted must be in full possession of the facts which he is quoted to prove, or upon which his opinion is based.

Regarding the capability of an authority to give expert evidence much has been said. It is well to remember, however, that the opinion of fact or judgment must be in the field of the authority's professional knowledge. The most eminent chemist in the United States would not be considered proper authority on an economic question; much less would the most eminent economist be considered good authority on some problem in chemistry. The President of the United States might be quoted as the highest authority on the political situation, while his opinion on some technical problem of engineering would fall before a counter opinion by an eminent engineer. In quoting an authority to establish an important point in evidence it is often advisable to show directly that he is unprejudiced, in full possession of the facts, and capable of giving expert testimony.

3. Evidence should be examined to determine whether there are attendant circumstances which will add to its weight.

It often happens that evidence which is good in itself is given still greater weight by some special circumstances. The law recognizes and gives much weight to "Declarations against Interest," and such declarations are as valuable in argumentation as in law. A declaration against interest is a statement of fact or opinion made by a party before the subject became a matter of controversy, which statement is now against the interest of the person making it. To illustrate, let us suppose that John D. Rockefeller had made a statement opposing the formation of monopolies. At present he wishes