There
are two argument sections; together they comprise one-half
of the test. Each section is 35 minutes long and contains
roughly 24 questions. This section is not as highly "timed"
as the games, so it is reasonable to set as your goal
the completion of the entire section. Unlike with games,
determining the level of difficulty of an argument is
itself difficult, so just start with the first question
and then work through the section.
INTRODUCTION
to LSAT TEST ARGUMENTS
An
argument, as used on the LSAT, is a presentation of facts
and opinions in order to support a position. Many arguments
will be fallacious. And many correct answers will be false!
This often causes students much consternation; they feel
that the correct answer should be true. But the arguments
are intended to test your ability to think logically.
Now logic is the study of the relationships between statements,
not of the truth of those statements. Being overly concerned
with finding the truth can be ruinous to your LSAT logic
score.
"2
OUT OF 5" RULE
Creating
a good but incorrect answer-choice is much harder than
developing the correct answer. For this reason, usually
only one attractive wrong answer-choice is presented.
This is called the "2 out of 5" rule. That is, only two
of the five answer-choices will have any real merit. Hence,
even if you don't fully understand an argument, you probably
can still eliminate the three fluff choices, thereby greatly
increasing your odds of answering the question correctly.
LOGIC
of LSAT ARGUMENTS
Although
in theory the questions on the LSAT argument section are
designed to be answered without any reference to formal
logic, the section is essentially a logic test. Some knowledge
of the fundamentals of logic, therefore, will give you
a definite advantage. Armed with this knowledge, you should
quickly notice that the arguments are fundamentally easy
and that most of them fall into a few basic categories.
In this section, we will study the logical structure of
arguments. In Logic II, we will symbolize and diagram
arguments in much the same way as we did with games.
Conclusions
Most
argument questions hinge, either directly or indirectly,
on determining the conclusion of the argument. The conclusion
is the main idea of the argument. It is what the writer
tries to persuade the reader to believe. Most often the
conclusion comes at the end of the argument. The writer
organizes the facts and his opinions so that they build
up to the conclusion. Sometimes, however, the conclusion
will come at the beginning of an argument, rarely does
it come in the middle, and occasionally, for rhetorical
effect, the conclusion is not even stated.
Example:
The
police are the armed guardians of the social order. The
blacks are the chief domestic victims of the American
social order. A conflict of interest exists, therefore,
between the blacks and the police.--Eldridge Cleaver,
Soul on Ice
Here
the first two sentences anticipate or set up the conclusion.
By changing the grammar slightly, the conclusion can be
placed at the beginning of the argument and still sound
natural:
A
conflict of interest exists between the blacks and the
police because the police are the armed guardians
of the social order and the blacks are the chief domestic
victims of the American social order.
The
conclusion can also be forced into the middle:
The
police are the armed guardians of the social order. So
a conflict of interest exists between the blacks and the
police because the blacks are the chief domestic victims
of the American social order.
It
is generally awkward, as in the previous paragraph, to
place the conclusion in the middle of the argument because
then it cannot be fully anticipated by what comes before
nor fully explained by what comes after. On the rare occasion
when a conclusion comes in the middle of an argument,
most often either the material that comes after it or
the material that comes before it is not essential.
In
summary: To find the conclusion, check the last sentence
of the argument. If that is not the conclusion, check
the first sentence. Rarely does the conclusion come in
the middle of an argument.
When
determining the meaning of a conclusion, be careful not
to read any more into it than what the author states.
Although arguments are not worded as precisely as games,
you still need to read them with more care than you would
use in your everyday reading.
As
with games, read the words and sentences of an argument
precisely, and use their literal meaning.
For
example, consider the meaning of some in the sentence
"Some of Mary's friends went to the party." It would be
unwarranted, based on this statement, to assume that some
of Mary's friends did not go to the party. Although it
may seem deceiving to say that some of Mary's friends
went to the party when in fact all of them did, it is
nonetheless technically consistent with the meaning of
some.
Some
means "at least one and perhaps all."
As
mentioned before, the conclusion usually comes at the
end of an argument, sometimes at the beginning, and rarely
in the middle. Writers use certain words to indicate that
the conclusion is about to be stated. Following is a list
of the most common conclusion indicators:
Conclusion
Indicators
| hence |
therefore |
| so |
accordingly |
| thus |
consequently |
| follows
that |
shows
that |
| conclude
that |
implies |
| as
a result |
means
that |
Most
often the conclusion of an argument is put in the form
of a statement. Sometimes, however, the conclusion is
given as a command or obligation.
Example:
All
things considered, you ought to vote.
Here,
the author implies that you are obliged to vote.
The
conclusion can even be put in the form of a question.
This rhetorical technique is quite effective in convincing
people that a certain position is correct. We are more
likely to believe something if we feel that we concluded
it on our own, or at least if we feel that we were not
told to believe it. A conclusion put in question form
can have this result.
Example:
The
Nanuuts believe that they should not take from Nature
anything She cannot replenish during their lifetime. This
assures that future generations can enjoy the same riches
of Nature that they have. At the current rate of destruction,
the rain forests will disappear during our lifetime. Do
we have an obligation to future generations to prevent
this result?
Here
the author trusts that the power of her argument will
persuade the reader to answer the question affirmatively.
Taking
this rhetorical technique one step further, the writer
may build up to the conclusion but leave it unstated.
This allows the reader to make up his own mind. If the
build-up is done skillfully, the reader will be more likely
to agree with the author, without feeling manipulated.
Example:
He
who is without sin should cast the first stone. There
is no one here who does not have a skeleton in his closet.
The
unstated but obvious conclusion here is that none of the
people has the right to cast the first stone.
When
determining the conclusion's scope be careful not to read
any more or less into it than the author states. LSAT
writers often create wrong answer-choices by slightly
overstating or understating the author's claim. Certain
words limit the scope of a statement. These words are
called quantifiers--pay close attention to them. Following
is a list of the most important quantifiers:
Quantifiers
| all |
except |
likely |
| some |
most |
many |
| only |
could |
no |
| never |
always |
everywhere |
| probably |
must |
alone |
Example:
Whether
the world is Euclidean or non-Euclidean is still an open
question. However, if a star's position is predicted based
on non-Euclidean geometry, then when a telescope is pointed
to where the star should be it will be there. Whereas,
if the star's position is predicted based on Euclidean
geometry, then when a telescope is pointed to where the
star should be it won't be there. This strongly indicates
that the world is non-Euclidean.
Which
one of the following best expresses the main idea of the
passage?
(A)
The world may or may not be Euclidean.
(B) The world is probably non-Euclidean.
(C) The world is non-Euclidean.
(D) The world is Euclidean.
(E) The world is neither Euclidean nor non-Euclidean.
Choice
(A) understates the main idea. Although the opening to
the passage states that we don't know whether the world
is non-Euclidean, the author goes on to give evidence
that it is non-Euclidean. Choice (C) overstates the main
idea. The author doesn't say that the world is non-Euclidean,
just that evidence strongly indicates that it is. In choice
(B), the word "probably" properly limits the scope of
the main idea, namely, that the world is probably non-Euclidean,
but we can't yet state so definitively. The answer is
(B).
Premises
Once
you've found the conclusion, most often everything else
in the argument will be either premises or "noise." The
premises provide evidence for the conclusion; they form
the foundation or infrastructure upon which the conclusion
depends. To determine whether a statement is a premise,
ask yourself whether it supports the conclusion. If so,
it's a premise. Earlier we saw that writers use certain
words to flag conclusions; likewise writers use certain
words to flag premises. Following is a partial list of
the most common premise indicators:
Premise
Indicators
| because |
for |
| since |
is
evidence that |
| if |
in
that |
| as |
owing
to |
| suppose |
inasmuch
as |
| assume |
may
be derived from |
Example:
Since
the incumbent's views are out of step with public opinion,
he probably will not be reelected.
Here
"since" is used to flag the premise that the incumbent's
positions are unpopular.
Suppressed
Premises
Most
arguments depend on one or more unstated premises. Sometimes
this indicates a weakness in the argument, an oversight
by the writer. More often, however, certain premises are
left tacit because they are too numerous, or the writer
assumes that his audience is aware of the assumptions,
or he wants the audience to fill in the premise themselves
and therefore be more likely to believe the conclusion.
Example:
Conclusion:
I knew he did it.
Premise:
Only a guilty person would accept immunity from prosecution.
The
suppressed premise is that he did, in fact, accept immunity.
The speaker assumes that his audience is aware of this
fact or at least is willing to believe it, so to state
it would be redundant and ponderous. If the unstated premise
were false (that is, he did not accept immunity), the
argument would not technically be a lie; but it would
be very deceptive. The unscrupulous writer may use this
ploy if he thinks that he can get away with it. That is,
his argument has the intended effect and the false premise,
though implicit, is hard to find or is ambiguous. Politicians
are not at all above using this tactic.
A
common question on the LSAT asks you to find the suppressed
premise of an argument. Finding the suppressed premise,
or assumption, of an argument can be difficult. However,
on the LSAT you have an advantage--the suppressed premise
is listed as one of the five answer-choices. To test whether
an answer-choice is a suppressed premise, ask yourself
whether it would make the argument more plausible. If
so, then it is very likely a suppressed premise.
Example:
American
attitudes tend to be rather insular, but there is much
we can learn from other countries. In Japan, for example,
workers set aside some time each day to exercise, and
many corporations provide elaborate exercise facilities
for their employees. Few American corporations have such
exercise programs. Studies have shown that the Japanese
worker is more productive than the American worker. Thus
it must be concluded that the productivity of American
workers will lag behind their Japanese counterparts, until
mandatory exercise programs are introduced.
The
conclusion of the argument is valid if which one of the
following is assumed?
(A)
Even if exercise programs do not increase productivity,
they will improve the American worker's health.
(B) The productivity of all workers can be increased by
exercise.
(C) Exercise is an essential factor in the Japanese worker's
superior productivity.
(D) American workers can adapt to the longer Japanese
work week.
(E) American corporations don't have the funds to build
elaborate exercise facilities.
The
unstated essence of the argument is that exercise is an
integral part of productivity and that Japanese workers
are more productive than American workers because they
exercise more. The answer is (C).
Counter-Premises
When
presenting a position, you obviously don't want to argue
against yourself. However, it is often effective to concede
certain minor points that weaken your argument. This shows
that you are open-minded and that your ideas are well
considered. It also disarms potential arguments against
your position. For instance, in arguing for a strong,
aggressive police department, you may concede that in
the past the police have at times acted too aggressively.
Of course, you will then need to state more convincing
reasons to support your position.
Example:
I
submit that the strikers should accept the management's
offer. Admittedly, it is less than what was demanded.
But it does resolve the main grievance--inadequate health
care. Furthermore, an independent study shows that a wage
increase greater than 5% would leave the company unable
to compete against Japan and Germany, forcing it into
bankruptcy.
The
conclusion, "the strikers should accept the management's
offer," is stated in the first sentence. Then "Admittedly"
introduces a concession; namely, that the offer was less
than what was demanded. This weakens the speaker's case,
but it addresses a potential criticism of his position
before it can be made. The last two sentences of the argument
present more compelling reasons to accept the offer and
form the gist of the argument.
Following
are some of the most common counter-premise indicators:
Counter-Premise
Indicators
| but |
despite |
| admittedly |
except |
| even
though |
nonetheless |
| nevertheless |
although |
| however |
in
spite of the fact |
As
you may have anticipated, the LSAT writers sometimes use
counter-premises to bait wrong answer-choices. Answer-choices
that refer to counter-premises are very tempting because
they refer directly to the passage and they are in part
true. But you must ask yourself "Is this the main point
that the author is trying to make?" It may merely be a
minor concession.
LSAT
TEST LOGIC II (DIAGRAMMING)
We
thoroughly covered diagramming in the game section. Diagramming
is also useful with arguments. However, the diagrams won't
be as elaborate as those used with games. In fact, in
these cases, the term "diagramming " is somewhat of a
misnomer. Rarely will we actually draw a diagram; instead
we will symbolize the arguments, much as we did the conditions
of the games.
Most
arguments are based on some variation of an if-then
statement. However, the if-then statement is often
embedded in other equivalent structures. We already studied
embedded if-then statements in the chapter on flow
charts. Still, we need to further develop the ability
to recognize these structures.
If-Then
A-->B
By
now you should be well aware that if the premise of an
if-then statement is true then the conclusion must
be true as well. This is the defining characteristic of
a conditional statement; it can be illustrated as follows:
A-->B
A
Therefore, B
This
diagram displays the if-then statement "A-->B,"
the affirmed premise "A," and the necessary conclusion
"B." Such a diagram can be very helpful in showing the
logical structure of an argument.
Example:
(If-then)
If
Jane does not study for the LSAT, then she will not score
well. Jane, in fact, did not study for the LSAT; therefore
she scored poorly on the test.
When
symbolizing games, we let a letter stand for an element.
When symbolizing arguments, however, we may let a letter
stand for an element, a phrase, a clause, or even an entire
sentence. The clause "Jane does not study for the LSAT"
can be symbolized as ~S, and the clause "she will not
score well" can be symbolized as ~W. Substituting these
symbols into the argument yields the following diagram:
~S-->~W
~S
Therefore, ~W
This
diagram shows that the argument has a valid if-then
structure. A conditional statement is presented, ~S-->~W;
its premise affirmed, ~S; and then the conclusion that
necessarily follows, ~W, is stated.
Embedded
If-Then Statements
Usually,
arguments involve an if-then statement. Unfortunately,
the if-then thought is often embedded in other
equivalent structures. In this section, we study how to
spot these structures.
Example:
(Embedded If-then)
John
and Ken cannot both go to the party.
At
first glance, this sentence does not appear to contain
an if-then statement. But it essentially says:
"if John goes to the party, then Ken does not."
Example:
(Embedded If-then)
Danielle
will be accepted to graduate school only if she does well
on the GRE.
Given
this statement, we know that if Danielle is accepted to
graduate school, then she must have done well on the GRE.
Note: Students often wrongly interpret this statement
to mean:
"If
Danielle does well on the GRE, then she will be accepted
to graduate school."
There
is no such guarantee. The only guarantee is that if she
does not do well on the GRE, then she will not be accepted
to graduate school.
"A
only if B" is logically equivalent to "if A, then B."
Affirming
the Conclusion Fallacy
A-->B
B
Therefore, A
Remember
that an if-then statement, A-->B, tells
us only two things: (1) If A is true, then B is true as
well. (2) If B is false, then A is false as well (contrapositive).
If, however, we know the conclusion is true, the if-then
statement tells us nothing about the premise. And
if we know that the premise is false (we will consider
this next), then the if-then statement tells us
nothing about the conclusion.
Example:
(Affirming the Conclusion Fallacy)
If
he is innocent, then when we hold him under water for
sixty seconds he will not drown. Since he did not die
when we dunked him in the water, he must be innocent.
The
logical structure of the argument above is most similar
to which one of the following?
(A)
To insure that the remaining wetlands survive, they must
be protected by the government. This particular wetland
is being neglected. Therefore, it will soon perish.
(B) There were nuts in that pie I just ate. There had
to be, because when I eat nuts I break out in hives, and
I just noticed a blemish on my hand.
(C) The president will be reelected unless a third candidate
enters the race. A third candidate has entered the race,
so the president will not be reelected.
(D) Every time Melinda has submitted her book for publication
it has been rejected. So she should not bother with another
rewrite.
(E) When the government loses the power to tax one area
of the economy, it just taxes another. The Supreme Court
just overturned the sales tax, so we can expect an increase
in the income tax.
To
symbolize this argument, let the clause "he is innocent"
be denoted by I, and let the clause "when we hold him
under water for sixty seconds he will not drown" be denoted
by ~D. Then the argument can be symbolized as
I-->~D
~D
Therefore, I
Notice
that this argument is fallacious: the conclusion "he is
innocent" is also a premise of the argument. Hence the
argument is circular--it proves what was already assumed.
The argument affirms the conclusion then invalidly uses
it to deduce the premise. The answer will likewise be
fallacious.
We
start with answer-choice (A). The sentence
"To
insure that the remaining wetlands survive, they must
be protected by the government"
contains
an embedded if-then statement:
"If
the remaining wetlands are to survive, then they must
be protected by the government."
This
can be symbolized as S-->P. Next, the sentence "This particular
wetland is being neglected" can be symbolized as ~P. Finally,
the sentence "It will soon perish" can be symbolized as
~S. Using these symbols to translate the argument gives
the following diagram:
S-->P
~P
Therefore, ~S
The
diagram clearly shows that this argument does not have
the same structure as the given argument. In fact, it
is a valid argument by contraposition.
Turning
to (B), we reword the statement "when I eat nuts, I break
out in hives" as
"If
I eat nuts, then I break out in hives." This in turn can
be symbolized as N-->H.
Next,
we interpret the clause "there is a blemish on my hand"
to mean "hives," which we symbolize as H. Substituting
these symbols into the argument yields the following diagram:
N-->H
H
Therefore, N
The
diagram clearly shows that this argument has the same
structure as the given argument. The answer, therefore,
is (B).
Denying
the Premise Fallacy
A-->B
~A
Therefore, ~B
The
fallacy of denying the premise occurs when an if-then
statement is presented, its premise denied, and then its
conclusion wrongly negated.
Example:
(Denying the Premise Fallacy)
The
senator will be reelected only if he opposes the new tax
bill. But he was defeated. So he must have supported the
new tax bill.
The
sentence "The senator will be reelected only if he opposes
the new tax bill" contains an embedded if-then statement:
"If the senator is reelected, then he opposes the new
tax bill." (Remember: "A only if B" is equivalent to "If
A, then B.") This in turn can be symbolized as R-->~T.
The sentence "But the senator was defeated" can be reworded
as "He was not reelected," which in turn can be symbolized
as ~R. Finally, the sentence "He must have supported
the new tax bill" can be symbolized as T. Using
these symbols the argument can be diagrammed as follows:
R-->~T
~R
Therefore, T
[Note:
Two negatives make a positive, so the conclusion ~(~T)
was reduced to T.] This diagram clearly shows that the
argument is committing the fallacy of denying the premise.
An if-then statement is made; its premise is negated;
then its conclusion is negated.
Transitive
Property
A-->B
B-->C
Therefore, A-->C
These
arguments are rarely difficult, provided you step back
and take a bird's-eye view. It may be helpful to view
this structure as an inequality in mathematics. For example,
5 > 4 and 4 > 3, so 5 > 3.
Notice
that the conclusion in the transitive property is also
an if-then statement. So we don't know that C is
true unless we know that A is true. However, if we add
the premise "A is true" to the diagram, then we can conclude
that C is true:
A-->B
B-->C
A
Therefore, C
As
you may have anticipated, the contrapositive can be generalized
to the transitive property:
A-->B
B-->C
~C
Therefore, ~A
Example:
(Transitive Property)
If
you work hard, you will be successful in America. If you
are successful in America, you can lead a life of leisure.
So if you work hard in America, you can live a life of
leisure.
Let
W stand for "you work hard," S stand for "you will be
successful in America," and L stand for "you can lead
a life of leisure." Now the first sentence translates
as W-->S, the second sentence as S-->L, and the conclusion
as W-->L. Combining these symbol statements yields the
following diagram:
W-->S
S-->L
Therefore, W-->L
The
diagram clearly displays the transitive property.
DeMorgan's
Laws
~(A
& B) = ~A or ~B
~(A or B) = ~A & ~B
If
you have taken a course in logic, you are probably familiar
with these formulas. Their validity is intuitively clear:
The conjunction A&B is false when either, or
both, of its parts are false. This is precisely what ~A
or ~B says. And the disjunction A or B is false
only when both A and B are false, which is precisely what
~A and ~B says.
You
will rarely get an argument whose main structure is based
on these rules--they are too mechanical. Nevertheless,
DeMorgan's laws often help simplify, clarify, or transform
parts of an argument. They are also useful with games.
Example:
(DeMorgan's Law)
It
is not the case that either Bill or Jane is going to the
party.
This
argument can be diagrammed as ~(B or J), which by the
second of DeMorgan's laws simplifies to (~B and ~J). This
diagram tells us that neither of them is going to the
party.
A
unless B
~B-->A
"A
unless B" is a rather complex structure. Though surprisingly
we use it with little thought or confusion in our day-to-day
speech.
To
see that "A unless B" is equivalent to "~B-->A," consider
the following situation:
Biff
is at the beach unless it is raining.
Given
this statement, we know that if it is not raining, then
Biff is at the beach. Now if we symbolize "Biff is at
the beach" as B, and "it is raining" as R, then the statement
can be diagrammed as ~R-->B.
CLASSIFICATION
In
Logic II, we studied deductive arguments. However, the
bulk of arguments on the LSAT are inductive. In this section
we will classify and study the major types of inductive
arguments.
An
argument is deductive if its conclusion necessarily follows
from its premises--otherwise it is inductive. In an inductive
argument, the author presents the premises as evidence
or reasons for the conclusion. The validity of the conclusion
depends on how compelling the premises are. Unlike deductive
arguments, the conclusion of an inductive argument is
never certain. The truth of the conclusion can range from
highly likely to highly unlikely. In reasonable arguments,
the conclusion is likely. In fallacious arguments, it
is improbable. We will study both reasonable and fallacious
arguments.
We
will classify the three major types of inductive reasoning--generalization,
analogy, and causal--and their associated fallacies.
Generalization
Generalization
and analogy, which we consider in the next section, are
the main tools by which we accumulate knowledge and analyze
our world. Many people define generalization as "inductive
reasoning." In colloquial speech, the phrase "to generalize"
carries a negative connotation. To argue by generalization,
however, is neither inherently good nor bad. The relative
validity of a generalization depends on both the context
of the argument and the likelihood that its conclusion
is true. Polling organizations make predictions by generalizing
information from a small sample of the population, which
hopefully represents the general population. The soundness
of their predictions (arguments) depends on how representative
the sample is and on its size. Clearly, the less comprehensive
a conclusion is the more likely it is to be true.
Example:
During
the late seventies when Japan was rapidly expanding its
share of the American auto market, GM surveyed owners
of GM cars and asked them whether they would be more willing
to buy a large, powerful car or a small, economical car.
Seventy percent of those who responded said that they
would prefer a large car. On the basis of this survey,
GM decided to continue building large cars. Yet during
the '80s, GM lost even more of the market to the Japanese.
Which
one of the following, if it were determined to be true,
would best explain this discrepancy.
(A)
Only 10 percent of those who were polled replied.
(B) Ford which conducted a similar survey with similar
results continued to build large cars and also lost more
of their market to the Japanese.
(C) The surveyed owners who preferred big cars also preferred
big homes.
(D) GM determined that it would be more profitable to
make big cars.
(E) Eighty percent of the owners who wanted big cars and
only 40 percent of the owners who wanted small cars replied
to the survey.
The
argument generalizes from the survey to the general car-buying
population, so the reliability of the projection depends
on how representative the sample is. At first glance,
choice (A) seems rather good, because 10 percent does
not seem large enough. However, political opinion polls
are typically based on only .001 percent of the population.
More importantly, we don't know what percentage of GM
car owners received the survey. Choice (B) simply states
that Ford made the same mistake that GM did. Choice (C)
is irrelevant. Choice (D), rather than explaining the
discrepancy, gives even more reason for GM to continue
making large cars. Finally, choice (E) points out that
part of the survey did not represent the entire public,
so (E) is the answer.
Analogy
To
argue by analogy is to claim that because two things are
similar in some respects, they will be similar in others.
Medical experimentation on animals is predicated on such
reasoning. The argument goes like this: the metabolism
of pigs, for example, is similar to that of humans, and
high doses of saccharine cause cancer in pigs. Therefore,
high doses of saccharine probably cause cancer in humans.
Clearly,
the greater the similarity between the two things being
compared the stronger the argument will be. Also the less
ambitious the conclusion the stronger the argument will
be. The argument above would be strengthened by changing
"probably" to "may." It can be weakened by pointing out
the dissimilarities between pigs and people.
Example:
Just
as the fishing line becomes too taut, so too the trials
and tribulations of life in the city can become so stressful
that one's mind can snap.
Which
one of the following most closely parallels the reasoning
used in the argument above?
(A)
Just as the bow may be drawn too taut, so too may one's
life be wasted pursuing self-gratification.
(B) Just as a gambler's fortunes change unpredictably,
so too do one's career opportunities come unexpectedly.
(C) Just as a plant can be killed by over watering it,
so too can drinking too much water lead to lethargy.
(D) Just as the engine may race too quickly, so too may
life in the fast lane lead to an early death.
(E) Just as an actor may become stressed before a performance,
so too may dwelling on the negative cause depression.
The
argument compares the tautness in a fishing line to the
stress of city life; it then concludes that the mind can
snap just as the fishing line can. So we are looking for
an answer-choice that compares two things and draws a
conclusion based on their similarity. Notice that we are
looking for an argument that uses similar reasoning, but
not necessarily similar concepts. In fact, an answer-choice
that mentions either tautness or stress will probably
be a same-language trap.
Choice
(A) uses the same-language trap--notice "too taut." The
analogy between a taut bow and self-gratification is weak,
if existent. Choice (B) offers a good analogy but no conclusion.
Choice (C) offers both a good analogy and a conclusion;
however, the conclusion, "leads to lethargy," understates
the scope of what the analogy implies. Choice (D) offers
a strong analogy and a conclusion with the same scope
found in the original: "the engine blows, the person dies";
"the line snaps, the mind snaps." This is probably the
best answer, but still we should check every choice. The
last choice, (E), uses language from the original, "stressful,"
to make its weak analogy more tempting. The best answer,
therefore, is (D).
Causal
Reasoning
Of
the three types of inductive reasoning we will discuss,
causal reasoning is both the weakest and the most prone
to fallacy. Nevertheless, it is a useful and common method
of thought.
To
argue by causation is to claim that one thing causes another.
A causal argument can be either weak or strong depending
on the context. For example, to claim that you won the
lottery because you saw a shooting star the night before
is clearly fallacious. However, most people believe that
smoking causes cancer because cancer often strikes those
with a history of cigarette use. Although the connection
between smoking and cancer is virtually certain, as with
all inductive arguments it can never be 100 percent certain.
Cigarette companies have claimed that there may be a genetic
predisposition in some people to both develop cancer and
crave nicotine. Although this claim is highly improbable,
it is conceivable.
There
are two common fallacies associated with causal reasoning:
1.
Confusing Correlation with Causation.
To
claim that A caused B merely because A occurred immediately
before B is clearly questionable. It may be only coincidental
that they occurred together, or something else may have
caused them to occur together. For example, the fact that
insomnia and lack of appetite often occur together does
not mean that one necessarily causes the other. They may
both be symptoms of an underlying condition.
2.
Confusing Necessary Conditions with Sufficient Conditions.
A
is necessary for B means "B cannot occur without A." A
is sufficient for B means "A causes B to occur, but B
can still occur without A." For example, a small tax base
is sufficient to cause a budget deficit, but excessive
spending can cause a deficit even with a large tax base.
A common fallacy is to assume that a necessary condition
is sufficient to cause a situation. For example, to win
a modern war it is necessary to have modern, high-tech
equipment, but it is not sufficient, as Iraq discovered
in the Persian Gulf War.
SEVEN
COMMON FALLACIES
Contradiction
A
Contradiction is committed when two opposing statements
are simultaneously asserted. For example, saying "it is
raining and it is not raining" is a contradiction. Typically,
however, the arguer obscures the contradiction to the
point that the argument can be quite compelling. Take,
for instance, the following argument:
"We
cannot know anything, because we intuitively realize that
our thoughts are unreliable."
This
argument has an air of reasonableness to it. But "intuitively
realize" means "to know." Thus the arguer is in essence
saying that we know that we don't know anything. This
is self-contradictory.
Equivocation
Equivocation
is the use of a word in more than one sense during an
argument. This technique is often used by politicians
to leave themselves an "out." If someone objects to a
particular statement, the politician can simply claim
the other meaning.
Example:
Individual
rights must be championed by the government. It is right
for one to believe in God. So government should promote
the belief in God.
In
this argument, right is used ambiguously. In the phrase
"individual rights" it is used in the sense of a privilege,
whereas in the second sentence right is used to mean proper
or moral. The questionable conclusion is possible only
if the arguer is allowed to play with the meaning of the
critical word right.
Circular
Reasoning
Circular
reasoning involves assuming as a premise that which you
are trying to prove. Intuitively, it may seem that no
one would fall for such an argument. However, the conclusion
may appear to state something additional, or the argument
may be so long that the reader may forget that the conclusion
was stated as a premise.
Example:
The
death penalty is appropriate for traitors because it is
right to execute those who betray their own country and
thereby risk the lives of millions.
This
argument is circular because "right" means essentially
the same thing as "appropriate." In effect, the writer
is saying that the death penalty is appropriate because
it is appropriate.
Shifting
The Burden Of Proof
It
is incumbent on the writer to provide evidence or support
for her position. To imply that a position is true merely
because no one has disproved it is to shift the burden
of proof to others.
Example:
Since
no one has been able to prove God's existence, there must
not be a God.
There
are two major weaknesses in this argument. First, the
fact that God's existence has yet to be proven does not
preclude any future proof of existence. Second, if there
is a God, one would expect that his existence is independent
of any proof by man.
Unwarranted
Assumptions
The
fallacy of unwarranted assumption is committed when the
conclusion of an argument is based on a premise (implicit
or explicit) that is false or unwarranted. An assumption
is unwarranted when it is false--these premises are usually
suppressed or vaguely written. An assumption is also unwarranted
when it is true but does not apply in the given context--these
premises are usually explicit.
Example:
(False Dichotomy)
Either
restrictions must be placed on freedom of speech or certain
subversive elements in society will use it to destroy
this country. Since to allow the latter to occur is unconscionable,
we must restrict freedom of speech.
The
conclusion above is unsound because
(A)
subversives do not in fact want to destroy the country
(B) the author places too much importance on the freedom
of speech
(C) the author fails to consider an accommodation between
the two alternatives
(D) the meaning of "freedom of speech" has not been defined
(E) subversives are a true threat to our way of life
The
arguer offers two options: either restrict freedom of
speech, or lose the country. He hopes the reader will
assume that these are the only options available. This
is unwarranted. He does not state how the so-called "subversive
elements" would destroy the country, nor for that matter,
why they would want to destroy it. There may be a third
option that the author did not mention; namely, that society
may be able to tolerate the "subversives" and it may even
be improved by the diversity of opinion they offer. The
answer is (C).
Appeal
To Authority
To
appeal to authority is to cite an expert's opinion as
support for one's own opinion. This method of thought
is not necessarily fallacious. Clearly, the reasonableness
of the argument depends on the "expertise" of the person
being cited and whether she is an expert in a field relevant
to the argument. Appealing to a doctor's authority on
a medical issue, for example, would be reasonable; but
if the issue is about dermatology and the doctor is an
orthopedist, then the argument would be questionable.
Personal
Attack
In
a personal attack (ad hominem), a person's character is
challenged instead of her opinions.
Example:
Politician:
How can we trust my opponent to be true to the voters?
He isn't true to his wife!
This
argument is weak because it attacks the opponent's character,
not his positions. Some people may consider fidelity a
prerequisite for public office. History, however, shows
no correlation between fidelity and great political leadership.
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