Books: Practical Argumentation
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George K. Pattee >> Practical Argumentation
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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.
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