THE ART OF LOGICAL THINKING/PART 19
CHAPTER XIX.
FALLACIES
A Fallacy is:
"An unsound argument or mode of arguing, which, while appearing to be
decisive of a question, is in reality not so; an argument or proposition
apparently sound, but really fallacious; a fallacious statement or proposition,
in which the error is not apparent, and which is therefore likely to mislead or
deceive; sophistry."
In
Deductive Reasoning, we meet with two classes of Fallacies; namely, (1)
Fallacious Premise; and (2) Fallacious Conclusion. We shall now consider each
of these in turn.
Fallacious
Premise is in effect an unwarranted assumption of premises.
One of the most common forms of this kind of Fallacy is known as "Begging
the Question," the principle of which is the assumption of a
fundamental premise which is not conceded; the unwarrantable assumption of that
which is to be proved; or the assumption of that by which it is to be proved,
without proving it. Its most common form is that of boldly stating some
unproven fact, authoritatively and positively, and then proceeding to use the
statement as the major premise of the argument, proceeding logically from that
point. The hearer perceiving the argument proceeding logically often fails to
remember that the premise has been merely assumed, without warrant
and without proof and omitting the hypothetical "if." One may
proceed to argue logically from the premise that "The moon is made of
green cheese," but the whole argument is invalid and fallacious because of
the fact that the person making it has "begged the question" upon an
unwarranted premise. Hyslop gives a good example of this form of fallacy in the
case of the proposition "Church and State should be united." Proof
being demanded the advocate proceeds to "beg the question" as
follows: "Good institutions should be united; Church and State are good
institutions; therefore, Church and State should be united." The
proposition that "Good institutions should be united" is fallacious,
being merely assumed and not proven. The proposition sounds reasonable, and few
will feel disposed to dispute it at first, but a little consideration will
show that while some good institutions may well be united, it
is not a general truth that all should be so.
"Begging
the Question" also often arises from giving a name to a thing,
and then assuming that we have explained the thing. This is a
very frequent practice with many people—they try to explain by
merely applying names. An example of this kind is had in the case of the person
who tried to explain why one could see through a pane of glass by saying
"because it is transparent." Or when one explains that the reason a
certain substance breaks easily is "because it is brittle." Moliere
makes the father of a dumb girl ask why his daughter is dumb. The physician
answers: "Nothing is more easy than to explain it; it comes from her
having lost the power of speech." "Yes, yes," objects the
father, "but the cause, if you please, why she has lost the power of
speech." The physician gravely replies: "All our best authors will
tell you that it is the impeding of the action of the tongue."
Jevons
says: "The most frequent way, perhaps, in which we commit this kind
of fallacy is to employ names which imply that we disapprove of something, and
then argue that because it is such and such, it must be condemned. When two
sportsmen fall out in some manner relating to the subject of game, one will, in
all probability, argue that the act of the other was 'unsportsmanlike,' and
therefore should not have been done. Here is to all appearance a correct
syllogism:
"No
unsportsmanlike act should be done; John Robinson's act was unsportsmanlike:
Therefore, John Robinson's act should not have been done.
"This
is quite correct in form; but it is evidently the mere semblance of an
argument. 'Unsportsmanlike' means what a sportsman should not do.
The point to be argued was whether the act fell within the customary definition
of what was unsportsmanlike."
Arising
from "Begging the Question," and in fact a class of the latter, is
what is called "Reasoning in a Circle." In this form of fallacy one
assumes as proof of a proposition the proposition itself; or, uses the
conclusion to prove the premise. For instance: "This man is a rascal
because he is a rogue; and he is a rogue because he is a rascal." Or,
"It is warm because it is summer; and it is summer because it is
warm." Or "He never drinks to excess, because he is never intemperate
in drinking."
Brooks
says: "Thus to argue that a party is good because it advocates good
measures, and that certain measures are good because they are advocated by so
excellent a party, is to reason in a circle. So when persons argue that their
church is the true one, because it was established by God, and then argue that
since it is the true church it must have been founded by God, they fall into
this fallacy. To argue that 'the will is determined by the strongest motive'
and to define the strongest motive as 'that which influences the will,' is to
revolve in a circle of thought and prove nothing. Plato commits this error when
he argues the immortality of the soul from its simplicity, and afterwards
attempts to prove its simplicity from its immortality." It needs care to avoid
this error, for it is surprising how easily one falls into it. Hyslop says:
"The fallacy of Reasoning in a Circle occurs mostly in long arguments
where it can be committed without ready detection.... When it occurs in a long
discourse it may be committed without easy discovery. It is likely to be
occasioned by the use of synonyms which are taken to express more than the
conception involved when they do not." What is called a Vicious Circle is
caused when the conclusion of one syllogism is used for a proposition in
another syllogism, which in its turn comes to be used as a basis for the first
or original syllogism.
Fallacious
Conclusion is in effect an unwarranted or irrelevant assumption
of a logical conclusion. There are many forms of this fallacy among which
are the following:
Shifting
ground, which consists in the pretence of proving one thing while in
reality merely a similar or related thing is being proved. In this class is the
argument that because a man is profane he must necessarily be dishonest; or that
because a man denies the inspiration of the Scriptures he must be an atheist.
Fallacious
Questioning, in which two or more related questions are asked, and
the answer of one is then applied to the other. For instance: "You
assert that the more civilized a community, the more silk-hats are to be found
in it?" "Yes." "Then, you state that silk-hats are the
promoters and cause of civilization in a community?" A question of this
kind is often so arranged that an answer either in the affirmative or the negative
will lead to a false or fallacious inference. For instance, the question once
asked a respectable citizen on the witness stand: "Have you stopped
beating your mother?" An answer of either "Yes" or
"No," was out of the question, for it would have placed the witness
in a false position, for he had never beaten his mother, nor been accused of
the same.
Partial
Proof, in which the proof of a partial or related fact is used to infer
a proof of the whole fact or a related one. For instance, it is fallacious to
argue that a man has been guilty of drunkenness by merely proving that he was
seen entering a saloon.
Appeal
to Public Opinion, in which the prejudices of the public are appealed to rather
than its judgment or reason. In politics and theological argument this
fallacy is frequent. It is no argument, and is reprehensible.
Appeal
to Authority, or Reverence, in which the reverence and respect of
the public for certain persons is used to influence their feelings in place of
their judgment or reason. For instance: "Washington thought so-and-so, and
therefore it must be right;" or "It is foolish to affirm that Aristotle
erred;" or "It has been believed by men for two thousand years, that,
etc;" or "What our fathers believed must be true." Appeals of
this kind may have their proper place, but they are fallacies nevertheless, and
not real argument.
Appeal
to Profession, in which an appeal is made to practices, principles or
professions of the opponent, rather than to reason or judgment. Thus we may
argue that a certain philosophy or religion cannot be sound or good, because
certain people who hold it are not consistent, or not worthy, moral or sober.
This argument is often used effectively against an opponent, and is valid
against him personally. But it is no valid argument against his philosophy or
belief, because he may act in violation of them, or he may change his practices
and still adhere to his beliefs—the two are not joined.
Appeal
to General Belief, in which an appeal is made to general or universal belief,
although the same may be unsupported by proof. This is quite common, but is no
real argument. The common opinion may be erroneous, as history proves. A few
centuries ago this argument could have been used in favor of the earth being
flat, etc. A half-century ago it was used against Darwin. Today it is being
used against other new ideas. It is a fallacy by its very nature.
Appeal
to Ignorance, in which an appeal is made to the ignorance of the opponent that
his conviction may follow from his inability to prove the contrary. It is
virtually no argument that: "So-and-so must be true, because you
cannot prove that it is not." As Brooks says: "To argue that
there is no material world, because we cannot explain how the mind knows it to
exist, is the celebrated fallacy of Hume in philosophy. The fact that we cannot
find a needle in a haystack is no proof that it is not there."
Introduction
of New Matter, also called Non Sequitur, in which matter is
introduced into the conclusion that is not in the premises. Hyslop gives the
following example of it: "All men are rational; Socrates is a
man; therefore, Socrates is noble." De Morgan gives the
following more complex example: "Episcopacy is of Scripture origin; The
Church of England is the only Episcopal church in England; therefore, the
church established is the church that ought to be supported."
Other
fallacies, resembling in some respects those above mentioned, are as follows:
Fallacy
of Ambiguous Terms, in which different meanings of the same word are used to produce
the fallacious argument. As Jevons says: "A word with two distinct
meanings is really two words."
Confusion
between Collective and General Meanings of a Term, of
which Jevons says: "It would be obviously absurd to argue that
because all the books in the British Museum Library are sure
to give information about King Alfred, therefore any particular book will be
sure to give it. By 'all the books in the British Museum Library,'
we mean all taken together. There are many other cases where
the confusion is not so evident, and where great numbers of people are unable
to see the exact difference."
Arguing
from the Collective to the General, in which the fallacy
consists of arguing that because something is true of the whole of a group of
things, therefore it is true of any of those things. Jevons says: "All the
soldiers in a regiment may be able to capture a town, but it is absurd to
suppose that therefore every soldier in the regiment could
capture the town single handed. White sheep eat a great deal more than black
sheep; but that is because there are so many more of them."
Uncertain
Meaning of a Sentence, from which confusion arises and fallacious argument may spring.
Jevons says: "There is a humorous way of proving that a cat must have
three tails: Because a cat has one tail more than no cat;
and no cat has two tails; therefore, any cat
has three tails." Here the fallacy rests upon a punning interpretation
of "no."
Proving
the Wrong Conclusion, in which the attempt to confuse conclusions is made,
with the result that some people will imagine that the case is
established. Jevons says: "This was the device of the Irishman, who was
charged with theft on the evidence of three witnesses, who had seen him do it;
he proposed to call thirty witnesses who had not seen
him do it. Equally logical was the defense of the man who was called a materialist,
and who replied, 'I am not a materialist; I am a barber.'"
Fallacy
of Unsuccessful Argument, in which is attempted the illogical
conclusion that because a certain argument has failed the opposite
conclusion is proven. This fallacy is quite common, especially in cases of
juries. One side fails to prove certain contentions, and the jury leaps to the
conclusion that the opposite contention must be correct. This is clearly
fallacious, for there is always the possibility of a third explanation.
In the case of a claim of alibi juries are apt to fall into
this fallacy. The failure of the attempt to establish an alibi is
often held to be in the nature of proof of the guilt of the accused. Old trial
lawyers assert that a failure to establish a claimed alibi tends
to injure the chance of the accused more than direct evidence against him.
Yet, as all logical reasoners will see, there is no logical validity in any
such inference. As Jevons has well said: "No number of failures in
attempting to prove a proposition really disprove it." At the end of
each failure the case simply stands in the same position as before the
attempt; i.e., "not proven."
All
Violations of the Rules of the Syllogism constitute fallacies,
as may be seen by forming a syllogism in violation of one or more of the rules.
The
logicians, particularly those of ancient times, took great pains to discover
and name new variations of fallacies, many of which were
hair-splitting in nature, and not worthy of being considered seriously. Some of
those which we have enumerated may possibly be open to the same criticism, but
we have omitted many of the worst offenders against practical common sense. An
understanding of the fundamental Laws of Reasoning is sufficient to expose and
unmask all fallacies, and such understanding is far more valuable than the
memorizing of the names of hair-splitting fallacies which
would not deceive a child.
In
addition to the above stated fallacies of Deductive Reasoning, there are other
fallacies which are met with in Inductive Reasoning. Let us briefly
consider them.
Hasty
and False Generalization is a common fallacy of this class.
Persons sometimes see certain qualities in a few individuals of a class, and
mistakenly infer that all the individuals in that class must
possess these same qualities. Travelers frequently commit this fallacy.
Englishmen visiting the United States for a few weeks have been known to
publish books upon their return home making the most ridiculous generalizations
regarding the American people, their assertions being based upon the
observation of a few scattered individuals, often not at all representative.
Americans traveling abroad commit similar errors. A flying trip through a
country does not afford the proper opportunity for correct generalization. As
Brooks says: "No hypothesis should be accepted as true until the facts are
so numerous that there can be no doubt of its being proved."
Fallacies
of Observation result from incorrect methods of observation among which
may be mentioned the following:
(1) Careless Observation, or
inexact perception and conception; (2) Partial Observation, in
which one observes only a part of the thing or fact, omitting the remainder,
and thus forming an incomplete and imperfect concept of the thing or fact;
(3) Neglect of Exceptions and Contradictory Facts, in which the
exceptions and contradictory facts are ignored, thereby giving undue importance
to the observed facts; (4) Assumption of Facts which are not
real facts, or the assumption of the truth of things which are untrue;
(5) Confusing of Inferences with Facts, which is most
unwarrantable.
Fallacies
of Mistaken Cause result from the assumption of a thing as a cause, when it is
not so, of which the following are familiar examples: Substituting the
Antecedent for the Cause, which consists in assuming a mere antecedent
thing for a cause of another thing. Thus one might assume that
the crowing of the cock was the cause of daybreak, because
it preceded it; or that a comet was the cause of the plague
which followed its appearance; or in the actual case in which a child reasoned
that doctors caused deaths, because observation had shown that
they always visited persons before they died; or that crops failed because a
President of a certain political party had been inaugurated a few months
before. Some fallacies of everyday reasoning are quite as illogical as those
just mentioned. Substituting the Symptom for the Cause, which
consists in assuming as a cause some mere symptom, sign or
incident of the real cause. To assume that the pimples of measles were
the cause of the disease, would be to commit a fallacy of this
kind. We have mentioned elsewhere the fallacy which would assume silk-hats to
be the cause of Civilization, instead of being a mere incident of the latter.
Politicians are fond of assuming certain incidents or signs of a period, as
being the causes of the prosperity, culture and advancement of
the period, or the reverse. One might argue, with equal force, that automobiles
were the causes of national prosperity, pointing to the fact that the more
automobiles to be seen the better the times. Or, that straw hats produced hot
weather, for similar reasons.
The
Fallacy of Analogy consists in assuming a resemblance or identity, where none
exists. We have spoken of this in another chapter. Brooks says, also: "It
is a fallacy to carry an analogy too far; as to infer from the parable of the
praying of the importunate woman that God resembles the unjust judge."
In
conclusion, we would call your attention to the following words from Jevons, in
which he expresses the gist of the matter: "It is impossible too often to
remind people that, on the one hand, all correct reasoning consists in
substituting like things for like things, and inferring that what is true
of one will be true of all which are similar to it in the points of resemblance
concerned in the matter. On the other hand, all incorrect reasoning
consists in putting one thing for another where there is not the requisite
likeness. It is the purpose of the rules of deductive and inductive logic
to enable us to judge as far as possible when we are thus rightly or wrongly
reasoning from some things to others."
FINIS.
END OF THIS BOOK.
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