  It has been seen that one who wishes to establish the truth or the falsity of a proposition must answer certain vital questions that are bound to arise in connection with it. Then, as different persons may answer these questions in different ways, it becomes necessary for him to convince his audience that his answers are correct. He must always beware of assertiveness. This defect occurs whenever a speaker or writer makes a statement but does not establish its truth. As simple denial is always sufficient answer to mere assertion, an unsupported statement is worthless. No one can hope to win in debate or change another's belief unless he can prove that what he says is true; he must substantiate with proof every statement that he makes, and show that no possibility for error or deceit can exist. In argumentation every statement not commonly accented as true must be proved. The following passage is a highly assertive bit of argument; its worthlessness is apparent. The decision of Congress to increase still further our already enormous navy is an injustice to every individual who contributes to the support of the national government. It is a crime to squander millions of money on a fleet that we do not need. Our navy to-day is more than the equal of any foreign armament that floats. Though second in number of ships, it ranks first in efficiency among all the navies of the world. No other country can boast of such marksmanship as our gunners display; no other country can boast of such armor plate as is to be found on our first-class battleships; not even England can successfully compete with us in seamanship and in general efficiency. Proof is "anything which serves either immediately or mediately to convince the mind of the truth or the falsehood of a fact or proposition." [Footnote: On Evidence, Best, p. 45.] Belief in a specific statement is induced by a presentation of pertinent facts, and usually by a process of reasoning whereby from the existence of these known facts, the conclusion, hitherto unaccepted, is reached. Those facts that have to do with the proposition under discussion are known as evidence. The process of combining facts and deriving an inference from them is known as reasoning. Evidence may be made up of the testimony of witnesses, the opinion of experts, knowledge derived from experience, the testimony of documents, or circumstances that are generally known to have existed. Reasoning is the process by which men form opinions, render judgments, explain events, or in any way seek new truths from established facts. In the following bit of proof, notice the facts that are stated, and see how, by a process of reasoning, they go to substantiate the idea that they are intended to prove:— New York hires two policemen where Nashville hires one, and pays them double the salary; yet Nashville is as peaceable and orderly as New York. In Nashville any child of school age can have a seat in the public schools all through the year; in New York there has been a shortage of seats for many years. Nashville has a filtered water supply; New York is going to have one as soon as the $12,000,000 filtration plant can be built at Jerome Park. Street car fares are five cents in both cities; in Nashville one can always get a seat; in New York one has to scramble for standing room. The southern city maintains hospitals, parks, food inspectors, and all other things common to New York and other large cities. Apparently, Nashville is giving as much to its inhabitants for six dollars per capita as New York for thirty-one. These facts can point to but one conclusion—that Nashville has a superior system of government. Since the first step in the generation of proof is the discovery of facts, the arguer should at the very outset become sufficiently familiar with the various kinds of evidence to estimate the value and strength of each idea that has a bearing upon the subject. I. EVIDENCE.There are two kinds of evidence: (a) direct, and (b) indirect or circumstantial. If a man sees a gang of strikers set fire to the buildings of their former employer, his evidence is direct. If, however, he only sees them stealthily leaving the buildings just before the fire breaks out, his evidence is indirect. In the latter case the man's testimony is direct evidence that the men were in the vicinity of the fire when it started, but it is indirect evidence that they perpetrated the crime. If a student who has failed to do good work throughout the term, and who has had little or no opportunity for special preparation, passes in a perfect paper at the close of an examination, the presumption is that he has received aid. The evidence on which this supposition rests is entirely circumstantial. But if some one saw the student obtaining aid, that fact would be direct evidence against him. Direct evidence, as a rule, is considered more valuable than indirect, but each kind is frequently sufficient to induce belief. The best possible kind of evidence, the kind that is least liable to contain error or falsehood, is a combination of both direct and indirect. Either one by itself may be untrustworthy. The unreliability of evidence given by eyewitnesses is shown by the conflicting stories they frequently tell concerning the same incident even when they are honestly attempting to relate the facts as they occurred. Also, it is always possible that the inferences drawn from a combination of circumstances may be entirely wrong. When, however, both kinds of evidence are available, each confirming the other and leading up to the same conclusion, then the possibility of error is reduced to a minimum. The opportunity of the college student for obtaining evidence in his argumentative work is limited. A lawyer before entering upon an important case often spends weeks and months in investigation; scientists sometimes devote a whole lifetime in trying to establish a single hypothesis. But the college student in preparing an argument must obtain his evidence in a few days. There are several sources at his disposal. The first available source is his fund of general knowledge and experience. If a man can establish a statement by saying that he personally knows it to be true, he has valuable proof. Then the people with whom the student comes in contact constitute another source of evidence. Anyone who can give information on a subject that is being investigated is a valuable witness. Especially in discussions on questions which pertain to college life, the opinions and experiences of college men and of prominent educators are unsurpassed as evidence. But the greatest source of evidence for the student of argumentation is the library. Here he may consult the best thought of all time in every branch of activity. He may review the opinions of statesmen, economists, educators, and scientists, and introduce as evidence their experiences and the results of their investigations. Here he may familiarize himself with the current events of the world, and draw his own conclusions as to their significance. In fact, a well equipped library treats of all subjects, however broad or narrow they may be, and furnishes evidence for all sorts of debatable questions. As not all evidence is equally valuable, a large part of the work of argumentation consists in applying tests to the evidence at hand for the sake of determining what facts are irrefutable, what are doubtful, and what are worthless. Moreover, one engaged in argumentation must test not only his own evidence but also that of the other side. No better method of refuting an opponent's argument exists than to show that the facts on which it rests are untrustworthy. Tests of evidence may be divided into two classes: tests of the source from which it comes, and tests of the quality of the evidence itself. A. TESTS OF THE SOURCE OF EVIDENCE.Since in courts of law, in college debate, and in all kinds of argumentation, facts are established by the testimony of witnesses, the sources of evidence are the witnesses who give it. The debater and the argumentative writer have not the opportunity, as has the lawyer, of producing the witnesses and permitting them to tell their own stories to the audience. He must himself relate the evidence; and, in order that it may be believed, he must tell whence it comes. The sources of evidence may be common rumor, newspapers, magazines, official documents, private citizens, or public officials. The extent to which these witnesses are accepted as trustworthy by the people before whom they are quoted determines in a large measure whether or not the evidence will be believed. Tests for determining the trustworthiness of witnesses will next be given. The first test of the source of evidence should be:— (1) Is the witness competent to give a trustworthy account of the matter under consideration? To answer this question, first determine whether the facts to be established are such that any ordinary person can speak concerning them with reasonable accuracy, or whether they can be understood only by persons who have received special training. A landsman could well testify that a naval battle had occurred, but only a man with nautical training could accurately describe the maneuvers of the ships and tell just how the engagement progressed. A coal heaver's description of a surgical operation would establish nothing, except perhaps the identity of the people and a few other general matters; only a person with a medical education could accurately describe the procedure. The testimony of any one but a naturalist would not even tend to prove the existence of an hitherto unknown species of animal life. A witness without technical knowledge cannot give reliable evidence on matters of a technical nature. Then, if it is found that the witness does possess the necessary technical training, or that no previous training is necessary, still further test his ability to give reliable evidence by asking whether he has had ample opportunity for investigating the facts to the existence of which he testifies. For even a skilled player sitting in the first base bleachers at a baseball game to criticise an umpire's decisions on balls and strikes is absurd; the opinion of a transient visitor to Panama on the methods used in digging the canal is not valuable; a traveler who has spent a single month in Japan cannot draw reliable conclusions on the merits and defects of its political structure. In not one of these cases has the opportunity for investigation been sufficient to render the witness able to give reliable evidence. A current magazine in discussing the weakness of testimony that comes from incompetent witnesses says:— 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? The human conscience is so constituted that many people deviate from the truth for no apparent reason whatever. Some are given to exaggeration; some habitually pretend to know that of which they are entirely ignorant; others are so inaccurate that everything they say is open to grave suspicion. If a witness is known to have been repeatedly dishonest or inaccurate in the past, little reliance should be placed in his testimony. "Yellow journalism," which is largely the reflection of common rumor, affords constant examples of witnesses that give questionable evidence. Ability and willingness to give exact evidence, an unprejudiced attitude, and a good reputation for honesty and accuracy are the qualities that should characterize the sources of evidence. If a writer or speaker is securing testimony from friends or acquaintances, the application of these tests is not difficult. If, however, the sources are books and periodicals, his work is harder; but to be successful, he must not shirk it. When one procures evidence from books, he should investigate the character and standing of the author. When one obtains it from signed articles in papers and magazines, he must consider both the author and the character of the publication. In the case of newspaper "stories" and editorials, one should find out on what general policy and principles the paper is conducted. A cautious arguer will always avoid, as far as he can, the use of evidence that comes from a doubtful source. If one finds that an opponent has used the testimony of questionable witnesses, he can, by exposing the fact, easily refute the argument. NECESSITY OF STATING SOURCES. It sometimes happens that an arguer fails to state the source of his evidence. This omission is usually fatal to success. No one is likely to put much confidence in statements that are introduced by such flimsy preambles as, "A certain statesman has declared"; "I have read somewhere"; "An acquaintance told me." Not only must evidence come from sources that seem good to the writer, but those sources must be satisfactory to the audience. In the last analysis the audience is the judge of what is credible and what is not. Moreover, if the evidence is of great importance, or is liable to be disputed, the arguer should show in a few words why the witness is especially reliable. B. INTERNAL TESTS OF EVIDENCE(1) Is the evidence consistent with (a) other evidence in the same argument; (b) known facts; (c) human experience? The requirement that every separate bit of evidence in an argument shall be consistent with every other bit of evidence in the same argument is too well understood to need explanation. One familiar with courts of law knows that a witness who contradicts himself is not believed. Furthermore, if the testimony of several witnesses for the same side is inconsistent, the case for that side is materially weakened. So it is in general debate: the arguer who wishes to succeed must not use evidence that is self-contradictory. His proof must "hang together"; his facts must all go to establish the same conclusion. A flagrant violation of this principle once occurred in a class-room debate. The speaker for the negative on the proposition, "Resolved, That freshmen should be ineligible for college teams," said that such a rule would deprive the freshmen of much- needed physical exercise. Later on, he said that just as many freshmen would receive injuries under this rule as without it, since they would take part in equally dangerous contests as members of freshmen teams. This contradiction ruined his argument. In the next place, evidence to be of any value whatever, must be consistent with what is known about the case. If an arguer is so careless as to make statements contradictory either to well- established facts or to facts easily proved, he cannot hope to attain the slightest measure of success. Only one guilty of gross neglect or absolute falsehood is likely to fall into such an error. At one time the story was circulated that, during his early life, Lincoln had been insane. In the following passage Ida M. Tarbell shows that the testimony on which this belief was founded is inconsistent with the known facts of the case, and is, therefore, palpably untrue:— "Mr. Thornton went on to say that he knew beyond a doubt that the sensational account of Lincoln's insanity was untrue, and he quoted from the House journal to show how it was impossible that, as Lamon says, using Herndon's notes, 'Lincoln went crazy as a loon, and did not attend the legislature in 1841-1842, for this reason'; or, as Herndon says, that he had to be watched constantly. According to the record taken from the journals of the House by Mr. Thornton, which have been verified in Springfield, Mr. Lincoln was in his seat in the House on that 'fatal first of January' when he is asserted to have been groping in the shadow of madness, and he was also there on the following day." Lincoln himself was an expert at detecting inconsistency wherever it existed. He won many of his lawsuits by the straightforward method of showing that the one or two vital statements on which the whole case of the opposition rested were false, inasmuch as they were inconsistent with well-established and incontrovertible facts. An instance of this sort is here described:— The most damaging evidence was that of one Allen, who swore that he had seen Armstrong strike Metzker about ten or eleven o'clock in the evening. When asked how he could see, he answered that the moon shone brightly. Under Lincoln's questioning he repeated the statement until it was impossible that the jury should forget it. With Allen's testimony unimpeached, conviction seemed certain. Lincoln's address to the jury was full of pathos. It was not as a hired attorney that he was there, he said, but to discharge a debt of friendship…. But Lincoln was not relying on sympathy alone to win his case. In closing he reviewed the evidence, showing that all depended on Allen's testimony, and this he said he could prove to be false. Allen never saw Armstrong strike Metzker by the light of the moon, for at the hour when he said he saw the fight, between ten and eleven o'clock, the moon was not in the heavens. Then procuring an almanac, he passed it to the judge and jury. The moon, which was on that night only in its first quarter, had set before midnight. [Footnote: The Life of Abraham Lincoln, Vol. I, p. 272. Ida M. Tarbell. The Doubleday & McClure Co.] An arguer should also be extremely careful to use evidence that on its face appears reasonable. Only an extremely credulous audience will accept ideas that run counter to human belief and experience. To attribute the occurrence of an event to supernatural causes would bring a smile of derision to any but a most ignorant and superstitious person. To attribute to men qualities and characteristics that human experience has shown they do not possess will bring equal discredit. No one is likely to accept evidence that contradicts his habits of thinking, that is contrary to what his life and experience have taught him is true. For this reason savage people are slow to believe the teachings of the Christian religion. For this reason it is difficult to make an audience believe that any one will deliberately and consistently work against his own interests, or follow any other unusual line of action. Evidence contrary to human experience may be true, but unless the exigencies of the argument demand its use, the arguer will do well to omit it entirely. If he is obliged to use it, he should make it appear as reasonable as he can, and also substantiate it with careful proof. Huxley appreciated the fact that evidence, to be believed, must be in accordance with man's experience when he wrote the following:— If any one were to try to persuade you that an oyster shell (which is also chiefly composed of carbonate of lime) had crystallized out of sea-water, I suppose you would laugh at the absurdity. Your laughter would be justified by the fact that all experience tends to show that oyster-shells are formed by the agency of oysters, and in no other way. The ease with which an argument that does not satisfy this requirement may be overthrown is clearly shown in the following extract from a student's forensic:— To say that the Cuban reconcentrados sunk the Maine in an effort to embroil the United States in a conflict with Spain is the veriest foolishness. There is not one scrap of documentary evidence to show that such was the case. Moreover, such an act would be unparalleled in the annals of history. It is unreasonable, contrary to all experience, that those oppressed people should have brought disaster, involving the destruction of property and the loss of many lives, upon the very nation that they were looking to for assistance. (2) Is the evidence first-hand or hearsay evidence? It is universally recognized that hearsay evidence is unreliable. A narrative is sure to become so garbled by passing from mouth to mouth that unless a witness can testify to a fact from his own personal knowledge the evidence he gives is worthy of little credence. There is sufficient chance for error when the person who witnessed the event relates the account himself; if the story is told by a second, and perhaps by a third person, it is likely to reflect but little of what really happened. Every one is familiar with the exaggerations of common rumor; it distorts facts so that they are unrecognizable. The works of Herodotus are untrustworthy because he frequently believed hearsay evidence. Since second-hand evidence both fails to establish anything worth while, if allowed to stand, and is easily overthrown even by a very little first-hand evidence, an arguer will do well to follow the custom of the law courts, and, as a rule, exclude it altogether. (3) Can the evidence be considered as especially valuable? (a) Hurtful admissions constitute an especially valuable kind of evidence. Since men are not wont to give evidence detrimental to their personal interest unless impelled to do so by conscientious scruples, any testimony damaging to the one who gives it is in all probability not only truthful, but also the result of careful investigation. When a practising physician admits that half the ailments of mankind are imaginary or so trivial as to need no medical attention, he is making a statement that is likely to injure his business; for this reason he is probably stating the result of his experience truthfully. If a railroad president says that in his opinion government supervision of railroads will benefit the public in the matter of rates and service, it may be taken for granted that he has given his honest belief, and that his natural reluctance to surrender any authority of his own has kept him from speaking carelessly. If a member of the United States Senate admits that that body is corrupt, and selfish, and untrustworthy, he is lowering his own rank; therefore it is reasonable to believe that he is speaking the truth according to his honest belief. The following is an example of this kind of evidence:— It was stated during the Manchurian campaign that the Jewish soldiers, of whom Kuropatkin had about 35,000, not only failed to hold their ground under fire, but by their timidity threw their comrades into panic. But good evidence can be cited from the correspondents of the Novoye Vremya, an Anti-Semitic organ, to the effect that among the Jews were found many "intrepid and intelligent soldiers," and that a number of them were awarded the St. George's cross for gallantry. [Footnote: The Nation, June 11, 1908.] It is hardly necessary to add that one who places especial reliance on this kind of evidence must be sure that the admission is really and not merely apparently contrary to the interest of the one who gives it. (b) Another particularly valuable kind of evidence is negative evidence, or the evidence of silence. Whenever a witness fails to mention an event which, if it had occurred, would have been of such interest to him that he might reasonably have been expected to have mentioned it, his silence upon the matter becomes negative evidence that the event did not occur. For many years no one suggested that Bacon wrote the Shakespearean plays; this absence of testimony to the belief that Bacon wrote them is strong evidence that such belief did not exist until recently, a fact that tends to discredit the Baconian theory of authorship. The fact that in the writings of Dickens and Thackeray no mention is made of the bicycle is negative evidence that the bicycle had not then come into use. That Moses nowhere in his writings speaks of life after death is negative evidence that the Hebrews did not believe in the immortality of the soul. If admittedly capable and impartial officials do not inflict penalties for foul playing during a football game, there is strong presumption that little or no foul playing occurred. The following paragraph, taken from a current magazine, shows how this kind of evidence may be handled very effectively:— A sharp controversy has been raging in the European press over the question whether Gambetta secretly visited Bismarck in 1878. Francis Laur, Gambetta's literary executor, has published an article asserting that he did, and giving details (rather vague, it must be admitted) of the conversation between the two statesmen. But he offers not a scrap of documentary proof. He is not even sure whether the interview took place at Friedrichsruh or at Varzin. This is rather disconcerting, especially in view of the fact that Bismarck never made the slightest reference in his reminiscences or letters to the visit of Gambetta, if it occurred, and that the minute Busch never mentioned it. [Footnote: The Nation, September 5, 1907] ARGUMENT FROM AUTHORITY.There is a particular kind of evidence frequently available for debaters and argumentative writers known as argument from authority. This evidence consists of the opinions and decisions of men who are recognized, to some extent at least, as authorities on the subjects of which they speak. An eminent scientist might explain with unquestioned certainty the operation of certain natural phenomena. A business man of wide experience and with well recognized insight into national conditions might speak authoritatively on the causes of business depressions. In religious matters the Bible is the highest authority for orthodox Christians; the Koran, for Mohammedans. In legal affairs the highest authorities are court decisions, opinions of eminent jurists, and the Constitution. If a certain college president is considered an authority in the matter of college discipline, then a quotation from him on the evils of hazing becomes valuable evidence for the affirmative of the proposition, "Hazing should be abolished in all colleges." If the arguer wishes to strengthen his evidence, he may do so by giving the president's reasons for condemning hazing; but he then departs from pure argument from authority. Pure argument from authority does not consist of a statement of the reasons involved; it asserts that something is true because some one who is acknowledged to be an authority on that subject says it is true. Argument from authority differs from other evidence in that it involves not merely investigation but also the exercise of a high degree of judgment. The statement that in 1902, in the United Kingdom, two hundred and ninety-five communities of from 8,000 to 25,000 inhabitants were without street-car lines is not argument from authority; the discovery of this truth involved merely investigation. On the other hand, if some reputable statesman or business man should say that street-car facilities in the United States excelled those of England, this evidence would be argument from authority; only through both investigation and judgment could such a statement be evolved. This kind of evidence is very strong when those addressed have confidence in the integrity, ability, and judgment of the person quoted. If, however, they do not know him, or if they do not consider him reliable, the evidence is of little value. Therefore, the test that an arguer should apply before using this kind of evidence is as follows:— Is the witness an acknowledged authority on the subject about which he speaks? Sometimes a short statement showing why the witness quoted is able to speak wisely and conclusively will render the evidence more valuable in the eyes of the audience. In the following example, notice how Judge James H. Blount used "authority" in proving that the Filipinos desired self-government:— Senator Dubois, of Idaho, who was a member of the Congressional party that visited the Philippines, has since said in the New York "Independent": All the Filipinos, with the exception of those who were holding positions under and drawing salaries from our Government, favor a government of their own. There is scarcely an exception among them…. There is nobody in the islands, no organization of any kind or description, which favors the policy of our Government toward them. Senator Newlands, of Nevada, also a member of the Congressional party aforesaid, has declared, in the number of this Review for December, 1905, that practically the whole people desire independence. Congressman Parsons, also a member of the same party, has since said: "There is no question that all the Filipino parties are now in favor of independence." Captain J. A. Moss, of the Twenty-fourth Infantry, a member of General Corbin's staff, is quoted by Mr. Bryan, in the "Commoner" of April 27th, 1906, as saying in an article published in a Manila paper while Mr. Bryan was in the islands, with reference to the wishes of "the great majority" of Filipinos, that "to please them, we cannot get out of the islands too soon." [Footnote: North American Review, Vol. CLXXXIV, p. 136.] II. REASONING.As has been said, proof consists of evidence and reasoning. Evidence has been considered first because this order corresponds to the way in which proof is usually generated; obviously, the discovery of facts precedes the process of reasoning which shows their significance. In some instances, however, this order is reversed: a man may form a theory and then hunt for the facts on which to base it; but in general, facts precede inferences. Since all people when they reason do not reach the same conclusion, it is very essential for a student to investigate the various processes of reasoning. Given exactly the same evidence, some men will draw one conclusion, some another. A current periodical recognizes this fact when it says:— How widely divergent may be conclusions drawn from the same source can be judged by contrasting these two statements: Messrs. Clark and Edgar declare that "where municipal ownership has been removed from the realm of philosophic discussion and put to the test of actual experience it has failed ingloriously"; Professor Parsons and Mr. Bemis on the contrary assert, to use Professor Parsons' words, "it is not public ownership, but private ownership, that is responsible for our periodic crisis and the ruin of our industries," and "it is not impossible that the elimination of the public service corporations through public ownership is one of the things that would do more to help along the process of making our cities fit." [Footnote: Outlook, July 27, 1907.] Because of the divergencies in the results produced by reasoning, a student should study with considerable care the various processes of arriving at a conclusion, so that he may be able to tell what methods are strong, what are weak, and what are fallacious. According to a common classification, there are two methods of reasoning: the inductive process, and the deductive process. 1. INDUCTIVE REASONING. When one carefully investigates his reasons for believing as he does, he often finds that he accepts a certain statement as true because he is familiar with many specific instances that tend to establish its truth. The belief that prussic acid is poisonous is based upon the large number of instances in which its deadly effect has been apparent. The fact that railroad men are exposed to injury is unquestioned because every one is familiar with the many accidents that occur each year. The statement that water freezes at thirty-two degrees Fahrenheit has been proved true by innumerable tests. This process of reasoning by which, from many specific instances, the truth of a general statement is established, is called induction. An example of inductive reasoning is found in the following passage:— Does the closing of the saloons affect appreciably the amount of drunkenness in the community? A comparison of the same town or city in successive years—one year under one system, and the next year under the other—furnishes a basis for accurate judgment. Evidence of this sort is all one way, and it seems to be conclusive. The tables prepared by the Massachusetts Bureau of Statistics of Labor, in 1905, under special instructions from the legislature, show that in Haverhill the average number of arrests per month under license was 81.63, under no-license, 26.50; in Lynn, under license, 315, under no-license, 117.63; in Medford, under license, 20.12, under no-license, 13.25; in Pittsfield, under license, 93.25, under no-license, 36.75; and in Salem, under license, 140.50, under no-license, 29.63. Such comparisons might be multiplied, but it is unnecessary. There is no escaping the conclusion that the closing of the saloons, under the Local Option system, does sensibly diminish the volume of drunkenness. [Footnote: Atlantic Monthly, Vol. XC, p. 437.] In using inductive reasoning, one must always be on his guard against drawing conclusions too hastily. It is never correct to conclude from a consideration of only a few instances that a general truth has been discovered. Further examination may show that the opinion first formed will not hold. Some people call all men dishonest because several acquaintances have not kept faith with them. Others are ready to believe that because they have made money in the stock market all can do likewise. Most superstitions arise through generalization from too few instances: those who have several times met misfortune on the thirteenth day of the month are apt to say that the thirteenth is always an unlucky day. Such reasoning as this shows the weakness of inductive argument: a conclusion is worthless if it is drawn from too few examples. Professor Fred Lewis Pattee, in writing on Errors in Reasoning, says:— Children and even adults often generalize from a single experience. A little boy cautioned me at one time to keep away from a certain horse, for "white horses always kick." An old Pennsylvania farmer laid down the law that shingles laid during the increase of the moon always curl up. He had tried it once and found out. A friend will advise you to take Blank's Bitters: "I took a bottle one spring and felt much better; they always cure." Physicians base their knowledge of medicines upon the observations of thousands of trained observers through many years, and not upon a single experience. Most people are prone to judge their neighbors from too slight acquaintance. If a man is late at an appointment twice in succession, someone is sure to say: "Oh, he's always late." This is poor thinking because it is bad judgment. Judgments should be made with care and from fullness of experience. [Footnote: The Adult Bible Class and Teacher Training Monthly, May, 1908, page 295.] The following quotation illustrates how often hasty generalizations create prejudice and sway public judgment:— There is an impression shared by many that the relation between the white and black races in this country is becoming less amicable and more and more surcharged with injustice. The basis for this impression is to be found in certain dramatic and sensational events, in particular the riots in Springfield, Illinois, and in Atlanta, Georgia. The memory of those events is becoming faint in many minds; but the impression they created remains. A dramatic event will have an effect upon public opinion which statistics, more significant but less picturesque, will altogether fail to produce. In the horror at the brief work of a mob the diminution in the annual number of lynchings is forgotten. The fundamental mistake in this is in the picking out of a startling episode or a reckless utterance and regarding it as typical. We do not arrive at the truth in that way. The Black Hand assassin does not furnish a true index to the Italian character. Aaron Burr is not an exhibit of the product of American Puritanism. So, if we wish to find out what American democracy has done with the negro, we do not search, if we are wise, into the chain-gang of Georgia or into the slums of New York. [Footnote: The Outlook, April 4, 1908.] The value of inductive reasoning depends upon the number of instances observed. Very seldom is it possible to investigate every case of the class under discussion. Of course this can sometimes be done. For instance, one may be able to state that all his brothers are college graduates, since he can speak authoritatively concerning each one of them. But usually an examination of every instance is out of the question, and whenever induction is based on less than all existing cases, it establishes only probable truth. From the foregoing it is seen that the tests for induction are two:— (1) Have enough instances of the class under consideration been investigated to establish the existence of a general law? (2) Have enough instances been investigated to establish the probable existence of a general law? 2. DEDUCTIVE REASONING. Deductive reasoning is the method of demonstrating the truth of a particular statement by showing that some general principle, which has previously been established or which is admitted to be true, applies to it. A stranger on coming to the United States might ask whether our postal system is a success. The answer would perhaps be, "Yes, certainly it is, for it is maintained by the government, and all our government enterprises are successful." When the metal thurium was discovered, a query doubtless arose as to whether it was fusible. It was then reasoned that since all metals hitherto known were fusible, and since thurium was a metal, undoubtedly it was fusible. Stated in clearer form, the reasoning in each case would be:— A. All our government enterprises are successful. B. The United States postal system is a government enterprise. C. Therefore the United States postal system is successful. A. All metals are fusible. B. Thurium is a metal. C. Therefore thurium is fusible. Such a series of statements is called a syllogism. A syllogism always consists of a major premise (A), a minor premise (B), and a conclusion (C). The major premise always states a general law; the minor premise shows that the general law applies to the particular case under consideration; and the conclusion is, in the light of the two premises, an established truth. The strength of deductive argument depends on two things: the truth of the premises and the framing of the syllogism. The syllogism must always be so stated that a conclusion is derived from the application of a general law to some specific instance to which the law obviously applies. In the next place, the premises must be true. If they are only probably correct, the conclusion is a mere presumption; if either one is false, the conclusion is probably false. But if the syllogism is correctly framed, and if both premises are true, the conclusion is irrefutable. As premises are facts that have first been established by induction, the relation between inductive and deductive reasoning is very close. In fact, deduction depends on induction for its very existence. To overthrow a deductive argument all that is necessary is to show the error in the inductive process that built up either one or both of the premises. The tests for deduction are:— (1) Are both premises true? (2) Is the fact stated in the minor premise an instance of the general law expressed in the major premise? In practical argumentation it is not always necessary or desirable to express a deductive argument in full syllogistic form. One premise is frequently omitted; the syllogism thus shortened is called an enthymeme. The reasoning then takes some such form as, "This man will fail in business because he is incompetent." The major premise, "All incompetent men fail in business," is understood, but is not expressed. The enthymeme constitutes as strong and forceful an argument as the syllogism, provided the suppressed premise is a well- established fact; but whenever this premise is not accepted as true, it must be stated and proved. The argument will then consist of the full syllogistic process. The following outline illustrates the chief difference between induction and deduction:— The game of football benefits the players physically, because (Induction.) 1. Football is known to have benefited Henry Harvey. 2. Football is known to have benefited Frank Barrs. 3. Football is known to have benefited Penn Armstrong. (Deduction.) 1. The game affords the players regular exercise. 2. The game takes them out in the open air. 3. The game develops the lungs. The deductive reasoning expressed in full would be:— (1) A. All games that afford the players regular exercise benefit them The reasoning given in (2) and (3) may be expressed in similar syllogisms. To test the inductive part of this argument, one should determine how well the three examples show the existence of a general law. To test the deductive part, he should ask whether the premises, both those stated and those suppressed, are admitted facts, or whether they need to be proved. If all reasoning were purely inductive or purely deductive, and if it always appeared in as simple a form as in the preceding illustration, one would have little difficulty in classifying and testing it. But frequently the two kinds appear in such obscure form and in such varied combinations that only an expert logician can separate and classify them. Because of this difficulty, it is worth while to know a second method of classification, one which is often of greater practical service than the method already discussed in assisting the arguer to determine what methods of reasoning are strong and what are weak. A knowledge of this classification is also very helpful to one who is searching for ways in which to generate proof. This method considers proof from the standpoint of its use in practical argument; it teaches not so much the different ways in which the mind may work, as the ways in which it must work to arrive at a sound conclusion. 1. ARGUMENT FROM ANTECEDENT PROBABILITY.The process of reasoning from cause to effect is known as the argument from antecedent probability. Whenever a thinking man is asked to believe a statement, he is much readier to accept it as true if some reasonable cause is assigned for the existence of the fact that is being established. The argument from antecedent probability supplies this cause. The reasoning may be from the past toward the present, or from the present toward the future. If an inspector condemns a bridge as unsafe, the question arises, "What has made it so?" If some one prophesies a rise in the price of railroad bonds, he is not likely to be believed unless he can show an adequate cause for the increase. In itself, the establishment of a cause proves nothing. A bridge may have been subjected to great strain and still be unimpaired. Though at present there may be ample cause for a future rise in the securities market, some other condition may intervene and prevent its operation. The assignment of a cause can at best establish merely a probability, and yet the laws of cause and effect are so fundamental that man is usually loath to believe that a condition exists or will exist, until he knows what has brought it about or what will bring it about. A course of reasoning which argues that a proposition is true because the fact affirmed is the logical result of some adequate cause is called argument from antecedent probability. Simple examples of this kind of reasoning are found in the following sentences: "It will rain because an east wind is blowing"; "As most of our officers in the standing army have been West Point graduates, the United States military system has reached a high standard of efficiency." The following are more extended illustrations:— It appears to have been fully established that, in certain industries, various economies in production—such as eliminating cross freights, concentrating the superintending force, running best plants to full capacity, etc.—can be made from production on a large scale, or, in other instances, through the combination of different establishments favorably located in different sections of the country. It is, of course, not to be expected that any one source of saving will be found applicable in all industries, nor that the importance of any will be the same in different industries; but in many industries enough sources of saving will be found to make combination profitable. This statement does not ignore the fact that there may be, in many instances, disadvantages enough to offset the benefits; but experience does seem to show that, in many cases, at least, the cost of manufacture, and distribution is materially lessened. Granting that these savings can be made, it is evident that the influence of Industrial Combinations might readily be to lower prices to consumers. [Footnote: Jeremiah W. Jenks, North American Review, June, 1901, page 907.] In attempting to prove that operas can be successfully produced in We have a poetic literature of marvelous richness. Only the Germans can lay claim to a lyric wealth as great as ours. The language we inherit is an extraordinarily rich one. A German authority credits it with a vocabulary three times as large as that of France, the poorest, in number of words, of all the great languages. With such an enormous fund of words to choose from it seems as if we should be able to express our thoughts not only with unparalleled exactness and subtlety, but also with unequalled variety of sound. Further it is probable that English surpasses the other three great languages of song, German, Italian, and French, in number of distinguishable vowel sounds, but in questions of ear authorities usually differ, and it is hazardous to claim in this an indubitable supremacy. It seems certain, however, that English has rather more than twice as many vowel sounds as Italian (the poorest language in this respect), which has only seven or eight. [Footnote: Scribner's, January, 1909, p. 42.] Since reasoning from antecedent probability can at best establish only a strong presumption, and since it is often not of sufficient weight to accomplish even this, an arguer, to be successful, must know the tests that determine how strong and how weak an argument of this sort is. He may apply these tests both to his own reasoning and to the reasoning of others. The first test is:— (1) Is the assigned cause of sufficient strength to produce the alleged effect? The significance of this question is at once apparent. In the case of a criminal prosecution, it asks whether the accused had sufficient motive for performing the deed. In connection with political and economic propositions that advocate a change in existing conditions, this test asks whether the new method proposed is sufficiently virile and far-reaching actually to produce the excellent results anticipated. A few years ago the advocates of free silver were maintaining that "sixteen to one" would be a sure cure for all poverty and financial distress. A careful application of this test would have materially weakened such an argument. Believers in reformatory rather than punitive methods of imprisonment say it is antecedently probable that kind treatment, healthful surroundings, and instruction in various directions will reclaim most criminals to an honest life. Before accepting or rejecting this argument, one should decide in his own mind whether or not such treatment is adequate to make a released convict give up his former criminal practices. If the argument stands the first test, the next question to ask is:— (2) May some other cause intervene and prevent the action of the assigned cause? During the spring of 1908 it was generally known that the Erie Railroad had no money with which to pay the interest that was about due on its outstanding bonds. Wall Street prophesied that the road would go into a receiver's hands. This result was extremely probable. Mr. Harriman, however, president of the Union Pacific, stepped in and by arranging for the payment of the interest saved the road from bankruptcy. This was an example of how an intervening cause prevented the action of the assigned cause. When Congress passed the Fifteenth Amendment to the Constitution, many people said that this legislation would inevitably cause the social, political, and financial ruin of the whole South. Since they did not take into consideration the intervening action of another cause, namely, drastic measures for negro disfranchisement by the white inhabitants of the South, their reasoning from antecedent probability was entirely erroneous. 2. ARGUMENT FROM SIGN.ARGUMENT FROM EFFECT TO CAUSE. The process of reasoning from effect to cause is called argument from sign. Since every circumstance must be the result of some preceding circumstance, the arguer tries to find the cause of some fact that is known to exist, and thereby to establish the existence of a hitherto unknown fact. For instance, when one sees a pond frozen over, he is likely to reason back to the cause of this condition and decide that there has been a fall in temperature, a fact that he may not have known before. The sight of smoke indicates the presence of fire. Human footprints in the snow are undoubted proof that someone has been present. In the following quotation, the recent prohibition movement in the South is said to be a sign that the voters wish to keep liquor away from the negro:— What is the cause of this drift toward prohibition in the South? The obvious cause, and the one most often given in explanation, is the presence of the negro. It is said that the vote for prohibition in the South represents exactly the same reasoning which excludes liquor from Indian reservations, shuts it out by international agreement from the islands of the Pacific, and excludes it from great areas in Africa under the British flag; and that, wherever there is an undeveloped race, the reasons for restrictions upon the liquor traffic become convincing. [Footnote: Atlantic Monthly, May, 1908, p. 632.] The strength of this kind of reasoning depends upon the closeness of the connection between the effect and the assigned cause. In testing argument from sign, one should ask:— (1) Is the cause assigned adequate to produce the observed effect? This test is precisely the same as the test of adequacy for antecedent probability. One could not maintain that the productiveness of a certain piece of ground was due entirely to the kind of fertilizer used on it, nor that a national financial upheaval was caused by the failure of a single unimportant bank. In each of these cases the cause suggested may have assisted in producing the result, but obviously it was not of itself adequate to be the sole cause. (2) Could the observed effect have resulted from any other cause than the one assigned? If several possible causes exist, then it is necessary to consider them all, and show that all the causes except the assigned cause did not produce the observed effect. If an employer who has been robbed discovers that one of his clerks has suddenly come into possession of a large sum of money, he may surmise that his clerk is a thief. This argument is valueless, however, unless he can show that his employee did not receive his newly acquired wealth through inheritance, fortunate investment, or some other reasonable method. But if no other reason than burglary or embezzlement can explain the presence of this money, the argument is very strong. One might greatly weaken the argument (quoted earlier) which assigned the cause of the recent prohibition movement in the South to the presence of the negro by showing that this action was not the result of the assigned cause, but largely of another cause. He might prove that during the debate in the Georgia Legislature upon the pending prohibitory bill, the negro was not once mentioned as a reason for the enactment of prohibition; and that the chief arguments in favor of prohibition were based upon the fact that the saloon element had formed a political ring in the South and were controlling the election of sheriffs, mayors, aldermen, and legislators. ARGUMENT FROM EFFECT TO EFFECT. Argument from sign also includes the process of reasoning from effect to effect through a common cause. This method consists of combining the process just described with the argument from antecedent probability. A reduction of wages in one cotton mill is a sign that there may be a reduction in other cotton mills. Here the reasoning goes from effect to effect, passing, however, though perhaps the reasoner is not aware that the process is so complex, through a cause common to both effects. In full, the reasoning would be: a reduction in the first mill is the result of the cause "hard times"; it is then antecedently probable that this cause will produce a similar reduction of wages in other mills. This method may be represented by the following figure:— Cause Only one effect is known; the other effect is inferred, first, by a process of reasoning from a known effect to an unknown cause, and secondly, by the process of reasoning from this assumed cause to an unknown effect. This method of reasoning is sound and legitimate when both effects have the same cause. Its weakness lies in the fact that it may be attacked on two sides: on the reasoning from effect to cause, and on the reasoning from cause to effect. If the connection can be broken in either process, the argument is overthrown. The tests to be used have already been given. 3. ARGUMENT FROM EXAMPLE.Argument from example is the name given to the process by which one reasons that what has been true under certain circumstances will again be true under the same or similar circumstances. In using this method of reasoning one argues that whenever several persons or things or conditions are alike in some respects, any given cause operating upon them will in each case produce the same effect; any line of action adopted by them will in each case have the same result. There are two divisions of argument from example. When the resemblance between the things compared is close, the process is called argument by generalization; when the resemblance is so slight that there can be no direct comparison, but only a comparison of functions, the process is called argument from analogy. ARGUMENT BY GENERALIZATION. If one finds that a certain mastiff becomes with training an excellent watch dog, he may reasonably take it for granted that training will produce the same result in another dog of the same breed. If a college student with certain pronounced physical and mental characteristics is known to be an exceptionally good football player, the athletic trainer is sure to reason by generalization that another student with these same characteristics would be a valuable addition to the team. Burke in his Speech on Conciliation uses this kind of reasoning when he says that just as Turkey and Spain have found it necessary to govern their distant possessions with a loose rein, so, too, England will be obliged to govern the American Colonies leniently. Benjamin Harrison used this method of argument in the following quotation:— That we give back to Porto Rico all the revenue derived from the customs we levy, does not seem to me to soften our dealings with her people. Our fathers were not mollified by the suggestion that the tea and stamp taxes would be expended wholly for the benefit of the colonies. It is to say: We do not need this money; it is only levied to show that your country is no part of the United States, and that you are not citizens of the United States, save at our pleasure. [Footnote: North American Review, January, 1901, p. 17.] Argument by generalization very rarely constitutes absolute proof. In dealing with things, it may do so in rare cases; in dealing with human actions, almost never. The reason why it can establish only a strong probability lies in a weakness in the process of reasoning. Notice that while this kind of argument apparently reasons directly from the example cited to the case in hand, there is in reality an intermediate step. This step is a general truth of which both the known fact and the fact to be proved must be instances. When it is argued that since one mastiff makes a good watch dog another mastiff will also make a good watch dog, the reasoning passes through the general statement, "All mastiffs make good watch dogs." Graphically the process might be represented thus:— General Law This method is very much like the method of reasoning from effect to effect, except that here the intermediate step does not cause, but merely accounts for the facts. In the illustration taken from Burke, the known fact is that neither Turkey nor Spain can govern their distant provinces despotically. The general law is that no country can govern a distant dependency harshly. The fact proved is that England cannot play the despot with the American Colonies. The weakness of this sort of reasoning is now easily seen. In the first place, there are few general laws governing human action that always hold true. In the second place, unless there is a very strong resemblance between the cases compared, unless they are alike in all essential particulars, they will not both be examples of the working of one general law. The following quotation points out an error that might be made from too hasty reasoning by example:— On August 23d the Southern Railway, which since 1902 had been paying 5 per cent. annual dividends on its preferred stock, voted to reduce those dividends from a 5 per cent. annual rate to one of 3. Five days later, on August 28th, the Erie Railroad, which had been paying 4 per cent … announced that it would pay no cash dividend this time, but would issue to the amount of the usual 4 per cent. dividend, what it called dividend warrants, which were practically notes at 4 per cent. redeemable in cash in 1907. It was natural that this action regarding dividends should have awakened much uneasiness…. To predict a similar cutting of dividends by other railway companies would, however, be unwarranted. The case of the Southern Railway and the Erie was peculiar. Each had been classed among the financially weak railways of the country. Both were reorganized from absolute railway wrecks, and in each the new scheme of capitalization was proposed to the markets at a time when recovery from the depression of 1893 had not made such progress as it had achieved when the greater companies, like the Union Pacific, were reorganized. The result was that, with both these railways, provisions of working capital and adjustment of liabilities to the possible needs of an active industrial future were inadequately made. [Footnote: Alexander D. Noyes, The Forum, October-December, 1907, p.198.] An excellent illustration of how to refute argument by generalization is found in the following quotation. It has been said that since England finds free trade beneficial, the United States should adopt the same policy. Mr. Reed, a leading advocate of protection, points out the weakness of this argument. |
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