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Rhetoric and Logic: The Great Debate
Induction or inductive reasoning, sometimes called inductive logic, is the
process of reasoning in which the premises of an argument are believed to
support the conclusion but do not entail it; i.e. they do not ensure its truth.
Induction is a form of reasoning that makes generalizations based on individual
instances. It is used to ascribe properties or relations to types based on an
observation instance (i.e., on a number of observations or experiences); or to
formulate laws based on limited observations of recurring phenomenal patterns.
Induction is employed, for example, in using specific propositions such as:
•This ice is cold. (or: All ice I have ever touched was cold.)
•This billiard ball moves when struck with a cue. (or: Of one hundred billiard
balls struck with a cue, all of them moved.)
...to infer general propositions such as:
•All ice is cold.
•All billiard balls move when struck with a cue.
Deductive reasoning is reasoning which uses deductive arguments to
move from given statements (premises), which are assumed to be true, to
conclusions, which must be true if the premises are true. An example of
deductive reasoning, given by Aristotle, is
• All men are mortal. (major premise)
• Socrates is a man. (minor premise)
• Socrates is mortal. (conclusion)
Deductive reasoning is often contrasted with inductive reasoning, which
reasons from a large number of particular examples to a general rule.
Logical Fallacies:
The best arguments are based in facts and reasoning. When a debater does not have the
facts or good reasoning on his/her side, the debater will often offer other arguments to
convince an audience. These other arguments often sound convincing, but they usually
include falsehoods, or mistakes in reasoning that are called logical fallacies. A debater who
plays to the crowd rather than to factual and logical argument is sometimes referred to as a
sophist, and their debating style is termed sophistry.
Sophists can still win debates, and all too often do. The better able an audience is to
distinguish between logical and factual argument on the one hand, and logical fallacy and
sophistry on the other, the better equipped that audience is not to be duped.
Following are some of the most common logical fallacies and erroneous debate techniques.
Proof by assertion is a logical fallacy in which a proposition is repeatedly restated
regardless of contradiction.
Sometimes this may be repeated until challenges dry up, at which point it is asserted as
fact due to its not being contradicted (argumentum ad nauseam). In other cases its
repetition may be cited as evidence of its truth, in a variant of the appeal to authority or
appeal to belief fallacies.
This logical fallacy is sometimes used as a form of rhetoric by politicians, or during a
debate as a filibuster. In its extreme form, it can also be a form of brainwashing. Modern
politics contains many examples of proof by assertions. This practice can be observed in
the use of political slogans, and the distribution of "talking points," which are collections of
short phrases that are issued to members of modern political parties for recitation to
achieve maximum message repetition. The technique is sometimes used in advertising.
The Big Lie: The technique is described in a saying, often attributed to Lenin, as "A lie told
often enough becomes the truth", although the user may not be intentionally promoting a lie
and may just believe an illogical or faulty proposition.
The argument from ignorance, also known as argumentum ad ignorantiam ("appeal
to ignorance") or argument by lack of imagination, is a logical fallacy in which it is
claimed that a premise is true only because it has not been proven false or is only false
because it has not been proven true.
The argument from personal incredulity, also known as argument from personal
belief or argument from personal conviction, refers to an assertion that because one
personally finds a premise unlikely or unbelievable, the premise can be assumed not to
be true, or alternatively that another preferred but unproven premise is true instead.
Both arguments commonly share this structure: a person regards the lack of evidence for
one view as constituting proof that another view is true. The types of fallacies discussed
in this article should not be confused with the reductio ad absurdum method of argument,
in which a valid logical contradiction of the form "A and not A" is used to disprove a
premise.
An argumentum ad populum (Latin: "appeal to the people"), in logic, is a fallacious
argument that concludes a proposition to be true because many or all people believe it; it
alleges that "If many believe so, it is so." In ethics this argument is stated, "If many find it
acceptable, it is acceptable.“
This type of argument is known by several names, including appeal to the masses,
appeal to belief, appeal to the majority, appeal to the people, argument by
consensus, authority of the many, and bandwagon fallacy, and in Latin also by the
names argumentum ad numerum ("appeal to the number"), and consensus gentium
("agreement of the clans"). It is also the basis of a number of social phenomena, including
communal reinforcement and the bandwagon effect, and of the Chinese proverb "three
men make a tiger":
“Three men make a tiger"
A government official, about to take a trip away from his office, worried that in his absence
his opponents and critics would undermine him to his king. He went to his king and asked
him whether he would hypothetically believe in one civilian's report that a tiger was roaming
the markets in the capital city, to which the king replied no. He asked what the king thought if
two people reported the same thing, and the king said he would begin to wonder. He then
asked, "what if three people all claimed to have seen a tiger?" The king replied that he would
believe in it. He reminded the king that the notion of a live tiger in a crowded market was
absurd, yet when repeated by numerous people, it seemed real. He urged the king to pay no
attention to those who would spread rumors about him while he was away. "I understand,"
the king replied, and the official left on his journey. Slanderous talk took place against him
when he was away. When he returned, the king indeed stopped seeing him.
Appeal to tradition, also known as proof from tradition, appeal to common practice,
argumentum ad antiquitatem, false induction, or the "is/ought" fallacy, is a common
logical fallacy in which a thesis is deemed correct on the basis that it correlates with some
past or present tradition. The appeal takes the form of "this is right because we've always
done it this way."
An appeal to tradition essentially makes two assumptions:
The old way of thinking was proven correct when introduced. In actuality this may be false
— the tradition might be entirely based on incorrect grounds.
The past justifications for the tradition are still valid at present. In cases where
circumstances have changed, this assumption may be false. The opposite of an appeal to
tradition is an appeal to novelty, claiming something is good because it is new.
Argument to moderation (Latin: argumentum ad temperantiam, also known as middle
ground, false compromise, gray fallacy, the golden mean fallacy) is a logical fallacy
which asserts that a compromise between two positions is correct.
The middle ground is often invoked when there
are sharply contrasting views that are deeply
entrenched. While an outcome that
accommodates both parties to some extent is
more desirable than an outcome that pleases
nobody, it is not necessarily correct.
The problem with the false compromise fallacy is
that it implies that both extremes are always
wrong, that only the middle ground is correct.
This is not always the case. Sometimes only X
or Y is acceptable, with no middle ground
possible. Additionally any position can be
invalidated by presenting one which is radically
opposite, thus forcing the compromise closer to
the desired conclusion.
In politics, this is part of the basis behind Overton Window Theory:
The concept of neutrality during wars, or various third way economic movements can
sometimes be considered an argument for taking the middle ground.
"Opinions on abortion range from banning it altogether to allowing it on demand; thus the
correct view is restricted abortions.“
The potential outcome of the Judgment of Solomon in the Old Testament — when
confronted with two women who each claimed the same baby to be their own — that the
baby be cut in half and each purported mother given half. This was of course a plan to
determine the true mother, but had it actually come down to cutting the baby in half, it
would have been done on the false pretense that half for one, half for the other — that is to
say, the middle ground — would have been a reasonable decision for the parties involved.
"On the one hand, we have the Theory of Evolution, and on the other, we have the theory
of Intelligent design. We should teach the controversy -- give both viewpoints equal time
and consideration, rather than preferring one over the other."
An ad hominem argument, also known as
argumentum ad hominem (Latin: "argument
to the man", "argument against the man")
consists of replying to an argument or factual
claim by attacking or appealing to a
characteristic or belief of the person making
the argument or claim, rather than by
addressing the substance of the argument or
producing evidence against the claim. The
process of proving or disproving the claim is
thereby subverted, and the argumentum ad
hominem works to change the subject. It is
most commonly used to refer specifically to the
ad hominem as abusive, sexist, racist, or
argumentum ad personam, which consists of
criticizing or attacking the person who
proposed the argument (personal attack) in
an attempt to discredit the argument. It is also
used when an opponent is unable to find fault
with an argument, yet for various reasons, the
opponent disagrees with it.
Other types of the ad hominem include the ad hominem circumstantial, or ad hominem
circumstantiae, an attack which is directed at the circumstances or situation of the arguer;
and the ad hominem tu quoque, which objects to an argument by characterizing the arguer
as a hypocrite.
Ad hominem arguments are always invalid in syllogistic logic, since the truth value of
premises is taken as given, and the validity of a logical inference is independent of the
person making the inference.
But, in law, the theory of evidence depends to a large degree on assessments of the
credibility of witnesses. Evidence that a purported eyewitness is unreliable, or has a motive
for lying, or that a purported expert witness lacks the claimed expertise can play a major role
in making judgments from evidence.
Argumentum ad hominem is the inverse of argumentum ad verecundiam, in which the arguer
bases the truth value of an assertion on the authority, knowledge or position of the person
asserting it. Hence, while an ad hominem argument may make an assertion less compelling,
by showing that the person making the assertion does not have the authority, knowledge or
position they claim, or has made mistaken assertions on similar topics in the past, it cannot
provide an infallible counterargument.
Appeal to motive is a pattern of argument which consists in challenging a thesis by calling
into question the motives of its proposer. It can be considered as a special case of the ad
hominem circumstantial argument. As such, this type of argument may be a logical fallacy. A
common feature of appeals to motive is that only the possibility of a motive (however small) is
shown, without showing the motive actually existed or, if the motive did exist, that the motive
played a role in forming the argument and its conclusion. Indeed, it is often assumed that the
mere possibility of motive is evidence enough.
Poisoning the well is a logical fallacy where adverse information about a target is
preemptively presented to an audience, with the intention of discrediting or ridiculing
everything that the target person is about to say. Poisoning the well is a special case of
argumentum ad hominem
In general usage, poisoning the well is the provision of any information that may produce
a biased result.
For example, if a woman tells her friend, "I think I might buy this beautiful dress", then
asks how it looks, she has "poisoned the well", as her previous comment could affect her
friend's response.
Ignoratio elenchi (also known as irrelevant conclusion or irrelevant thesis) is the
informal fallacy of presenting an argument that may in itself be valid, but does not address
the issue in question. Aristotle believed that an ignoratio elenchi is a mistake made by a
questioner while attempting to refute a respondent's argument. He called it an ignorance of
what makes for a refutation. In fact, Aristotle goes so far as to say that all logical fallacies
can be reduced to what he calls ignoratio elenchi.
Red herring
Similar to ignoratio elenchi, a red herring is an argument, given in reply, that does not
address the original issue. Critically, a red herring is a deliberate attempt to change the
subject or divert the argument. This is known formally in the English vocabulary as
Digression which is a neutrally connotated "Red herring".
Blueback Herring
Examples
• Baseball player Mark McGwire just retired. He's such a nice guy, and he gives a lot of money
to all sorts of charities. Clearly, he will end up in the Hall of Fame.
The conclusion is ignoratio elenchi, since friendliness and charity are not the main qualifications
for induction into the Hall of Fame.
• I should not pay a fine for reckless driving. There are actual dangerous criminals on the
street, and the police should be chasing them instead of harassing a decent tax-paying citizen
like me.
The existence of worse criminals is a secondary issue which has no bearing on whether the
driver deserves a fine for recklessness. If the speaker were deliberately attempting to divert the
issue, this would be an example of a red herring. While the argument about how the police
should spend their time may have merit, the question of whom the police should prioritize
pursuing and the question of what should be done with those the police have caught are
separate questions.
A straw man argument is an informal fallacy based on misrepresentation of an opponent's
position. To "set up a straw man" or "set up a straw man argument" is to describe a position
that superficially resembles an opponent's actual view but is easier to refute, then attribute
that position to the opponent (for example, deliberately overstating the opponent's position).
A straw man argument can be a successful rhetorical technique (that is, it may succeed in
persuading people) but it carries little or no real evidential weight, because the opponent's
actual argument has not been refuted.
Its name is derived from the practice of using straw men in
combat training. In such training, a scarecrow is made in the
image of the enemy with the single intent of attacking it. Such
a target is, naturally, immobile and does not fight back, and is
not as realistic to test skill against compared to a live and
armed opponent.
Argumentum ad baculum (Latin: argument to the cudgel or appeal to the stick), also known
as appeal to force, is an argument where force, coercion, or the threat of force, is given as a
justification for a conclusion. It is a specific case of the negative form of an argument to the
consequences.
A fallacious logical argument based on argumentum ad baculum generally has the following
argument form:
If x does not accept P as true, then Q.
Q is a punishment on x.
Therefore, P is true.
For example:
If you do not believe that Jesus Christ is God, you will go to hell. Therefore, Jesus
Christ is God. (Pascal’s Wager)
Other Examples
"I don't remember owing you any money. If I do not pay this supposed debt, you will beat me
up and hurt my family. Therefore I do owe you some money."
"Our political views are right and you should agree with them, because if you do not we will
put you in a Gulag."