FROM ANALYSIS TO ARGUMENT
SESSION #2
III. LOGOS
In arguments, premises are offered to provide support for the conclusion. Logic is about whether
or not the support is adequate. If the logic is not adequate, it doesn’t matter what the premises are
about; they won’t provide adequate support for the conclusion.
Logic is a formal system of analysis that helps writers invent, demonstrate, and prove arguments.
It works by testing propositions against one another to determine their accuracy. People often think
they are using logic when they avoid emotion or make arguments based on their common sense,
such as "Everyone should look out for their own self-interests" or "People have the right to be
free." However, unemotional or common sense statements are not always equivalent to logical
statements. To be logical, a proposition must be tested within a logical sequence.
The most famous logical sequence, called the syllogism, was developed by the Greek philosopher
Aristotle. His most famous syllogism is:
Premise 1: All men are mortal.
Premise 2: Socrates is a man.
Conclusion: Therefore, Socrates is mortal.
In this sequence, premise 2 is tested against premise 1 to reach the logical conclusion. Within this
system, if both premises are considered valid, there is no other logical conclusion than determining
that Socrates is a mortal.
Before using logic to reach conclusions, it is helpful to know some important vocabulary related
to logic.
-
-
Premise: Proposition used as evidence in an argument.
Conclusion: Logical result of the relationship between the premises. Conclusions serve as
the thesis of the argument.
Argument: The assertion of a conclusion based on logical premises.
Syllogism: The simplest sequence of logical premises and conclusions, devised by
Aristotle.
Enthymeme: A shortened syllogism which omits the first premise, allowing the audience
to fill it in. For example, "Socrates is mortal because he is a human" is an enthymeme
which leaves out the premise "All humans are mortal."
Induction: A process through which the premises provide some basis for the conclusion.
Deduction: A process through which the premises provide conclusive proof for the
conclusion.
Reaching Logical Conclusions
Reaching logical conclusions depends on the proper analysis of premises. The goal of a syllogism
is to arrange premises so that only one true conclusion is possible.
Consider the following premises:
Premise 1: Non-renewable resources do not exist in infinite supply.
Premise 2: Coal is a non-renewable resource.
From these two premises, only one logical conclusion is available: Conclusion: Coal does not exist
in infinite supply.
Often logic requires several premises to reach a conclusion.
Premise 1: All monkeys are primates.
Premise 2: All primates are mammals.
Premise 3: All mammals are vertebrate animals. Conclusions: Monkeys are vertebrate animals.
Logic allows specific conclusions to be drawn from general premises. Consider the following
premises:
Premise 1: All squares are rectangles.
Premise 2: Figure 1 is a square.
Conclusion: Figure 1 is also a rectangle.
EXERCISE 4
Identify the logic of the following statements. Identify the premises and the conclusion to analyse
the conclusion
What conclusion can be drawn on the basis of these two statements?
1. All travellers are people.
All tourists are travellers.
a.
b.
c.
d.
All tourists are people
Some people are not tourists
Some tourists are not people
All people are tourists
2. No bosses are employees.
All elderly are bosses.
a.
b.
c.
d.
No elderly are employees
All elderly are employees
All employees are elderly
Some elderly are employees
3. No waterrats are swimmers.
All bikeriders are swimmers.
a.
b.
c.
d.
No bikeriders are waterrats
All waterrats are bikeriders
All bikeriders are waterrats
Some bikeriders are waterrats
4. All crumbs are parts.
All pieces are crumbs.
a. Some pieces are not parts
b. All parts are pieces
c. All pieces are parts
d. Some parts are not pieces
5. No bananas are kiwis.
All apples are bananas.
a. Some apples are kiwis
b. No apples are kiwis
c. All kiwis are apples
d. All apples are kiwis
Syllogistic Fallacies
The syllogism is a helpful tool for organizing persuasive logical arguments. However, if used
carelessly, syllogisms can instil a false sense of confidence in unfounded conclusions. The
examples in this section demonstrate how this can happen.
Example D:
Logic requires decisive statements in order to work. Therefore, this syllogism is false:
Premise 1: Some quadrilaterals are squares.
Premise 2: Figure 1 is a quadrilateral.
Conclusion: Figure 1 is a square.
This syllogism is false because not enough information is provided to allow a verifiable
conclusion. Figure 1 could just as likely be a rectangle, which is also a quadrilateral.
Example E:
Logic can also mislead when it is based on premises that an audience does not accept. For instance:
Premise 1: People with red hair are not good at checkers.
Premise 2: Bill has red hair.
Conclusion: Bill is not good at checkers.
Within the syllogism, the conclusion is logically valid. However, the syllogism itself is only true
if an audience accepts Premise 1, which is very unlikely. This is an example of how logical
statements can appear accurate while being completely false.
Example F:
Logical conclusions also depend on which factors are recognized and ignored by the premises.
Therefore, premises that are correct but that ignore other pertinent information can lead to incorrect
conclusions.
Premise 1: All birds lay eggs.
Premise 2: Platypuses lay eggs.
Conclusion: Platypuses are birds.
It is true that all birds lay eggs. However, it is also true that some animals that are not birds lay
eggs. These include fish, amphibians, reptiles, and a small number of mammals (like the platypus
and echidna). To put this another way: laying eggs is not a defining characteristic of birds. Thus,
the syllogism, which assumes that because all birds lay eggs, only birds lay eggs, produces an
incorrect conclusion.
A better syllogism might look like this:
Premise 1: All mammals have fur.
Premise 2: Platypuses have fur.
Conclusion: Platypuses are mammals.
Fur is indeed one of the defining characteristics of mammals—in other words, there are not nonmammal animals who also have fur. Thus, the conclusion here is more firmly-supported.
In sum, though logic is a very powerful argumentative tool and is far preferable to a disorganized
argument, logic does have limitations. It must also be effectively developed from a syllogism into
a written piece.
Logical Fallacies
Fallacies are errors or tricks of reasoning that will undermine the logic of your argument. Its
use undercuts the validity and soundness of any argument. At the same time, fallacious reasoning
can damage the credibility of the speaker or writer and improperly manipulate the emotions of the
audience or reader. This is a consideration you must keep in mind as a writer who is trying to
maintain credibility (ethos) with the reader. Moreover, being able to recognize logical fallacies in
the speech and writing of others can greatly benefit you as both a college student and a participant
in civic life. Not only does this awareness increase your ability to think and read critically—and
thus not be manipulated or fooled—but it also provides you with a strong basis for counter
arguments. (rebut, disapprove done after summarizing the opposing opinion which called the
counterargument: completely or partly true by admitting the partial truth and then go on to explain
why the opposing opinion is untrue or unimportant. Common expressions are: It is true that X, yet
Y; White X, Y; Granted X, but Y; Admittedly X. However Y)
Even more important, using faulty reasoning is unethical and irresponsible. Using logical fallacies
can be incredibly tempting. The unfortunate fact is they work. Every day—particularly in politics
and advertising—we can see how using faults and tricks of logic effectively persuade people to
support certain individuals, groups, and ideas and, conversely, turn them away from others.
Furthermore, logical fallacies are easy to use. Instead of doing the often difficult work of carefully
supporting an argument with facts, logic, and researched evidence, the lazy debater turns routinely
to the easy path of tricky reasoning. Human beings too often favour what is easy and effective,
even if morally questionable, over what is ethical, particularly if difficult. However, your college
professors’ task is not to teach you how to join the Dark Side. Their job is to teach you how to
write, speak, and argue effectively and ethically. To do so, you must recognize and avoid the
logical fallacies.
What Are Formal Fallacies?
Most formal fallacies are errors of logic: The conclusion does not really “follow from” (is not
supported by) the premises. Either the premises are untrue, or the argument is invalid. Below is an
example of an invalid deductive argument:
Premise: All black bears are omnivores.
Premise: All raccoons are omnivores.
Conclusion: All raccoons are black bears.
Bears are a subset of omnivores. Raccoons also are a subset of omnivores. But these two subsets
do not overlap, and that fact makes the conclusion illogical. The argument is invalid—that is, the
relationship between the two premises does not support the conclusion.
“Raccoons are black bears” is instantaneously recognizable as fallacious and may seem too silly
to be worth bothering about. However, that and other forms of poor logic play out on a daily basis,
and they have real world consequences. Below is an example of a common fallacious argument:
Premise: All Arabs are Muslims.
Premise: All Iranians are Muslims.
Conclusion: All Iranians are Arabs.
This argument fails on two levels. First, the premises are untrue because, although many Arabs
and Iranians are Muslim, not all are. Second, the two ethnic groups (Iranians and Arabs) are sets
that do not overlap; nevertheless, the two groups are confounded because they (largely) share one
quality in common (being Muslim). One only has to look at comments on the web to realize that
the confusion is widespread and that it influences attitudes and opinions about US foreign policy.
The logical problems make this both an invalid and an unsound argument.
Type of fallacies
TYPE OF
FALLACIES
1
Slippery
Slope
DESCRIPTION
This is a conclusion based
on the premise that if A
happens, then eventually
through a series of small
steps, through B, C,..., X,
Y, Z will happen, too,
basically equating A and
Z. So, if we don't want Z
to occur, A must not be
allowed to occur either.
EXAMPLE
If we ban Hummers
because they are bad for
the environment
eventually the
government will ban all
cars, so we should not
ban Hummers.
REASONING
The author is equating banning
Hummers with banning all cars, which is
not the same thing.
Conclusion: we should not ban hummers
Premise 1: Do not ban hummers for the
environment
Premise 2: the government will ban all
car
Hasty
This is a conclusion based
Generalizat on insufficient or biased
ion
evidence. In other words,
you are rushing to a
conclusion before you
have all the relevant facts
Post hoc
This is a conclusion that
ergo
assumes that if 'A'
propter
occurred after 'B' then 'B'
hoc
must have caused 'A.'
Even though it's only the
first day, I can tell this is
going to be a boring
course.
The author is basing his evaluation of the
entire course on only the first day. To
make a fair and reasonable evaluation the
author has to have sufficient evidence to
base a conclusion on.
I drank bottled water and
now I am sick, so the
water must have made me
sick
The author assumes that if one event
chronologically follows another the first
event must have caused the second.
But the illness could have been caused
by other causes
4
Genetic
Fallacy
The Volkswagen Beetle
is an evil car because it
was originally designed
by Hitler's army.
In this example the author is equating the
character of a car with the character of
the people who built the car. However,
the two are not inherently related.
5
Begging the The conclusion that the Filthy and polluting coal Arguing that coal pollutes the earth and
Claim
writer should prove is should be banned
thus should be banned would be logical.
validated within the
But the very conclusion that should be
claim
proved, that coal causes enough
pollution to warrant banning its use, is
already assumed in the claim by
referring to it as "filthy and polluting."
6
Circular
Argument
This restates the
argument rather than
actually proving it
7
Either/or
This is a conclusion that We can either stop using
oversimplifies
the cars or destroy the earth.
argument by reducing it
to only two sides or
choices.
2
3
This conclusion is based
on an argument that the
origins of a person, idea,
institute, or theory
determine its character,
nature, or worth.
George Bush is a good The conclusion that Bush is a "good
communicator because he communicator" and the evidence used
speaks effectively
to prove it "he speaks effectively" are
basically the same idea. Specific
evidence such as using everyday
language, breaking down complex
problems, or illustrating his points with
humorous stories would be needed to
prove either half of the sentence
the two choices are presented as the only
options, yet the author ignores a range of
choices in between such as developing
cleaner technology, car-sharing systems
for necessities and emergencies, or better
community planning to discourage daily
driving.
8
Ad
hominem
This is an attack on the
character of a person
rather than his or her
opinions or arguments
Green Peace's strategies
aren't effective because
they are all dirty, lazy
hippies
the author doesn't even name particular
strategies Green Peace has suggested,
much less evaluate those strategies on
their merits. Instead, the author attacks
the characters of the individuals in the
group.
9
Ad
populum/
This is an appeal that
presents
what
most
people, or a group of
people think, in order to
persuade one to think the
same way. Getting on the
bandwagon is one such
instance of an ad populum
appeal
If you were a true
American you would
support the rights of
people
to
choose
whatever vehicle they
want.
the author equates being a "true
American," a concept that people want to
be associated with, particularly in a time
of war, with allowing people to buy any
vehicle they want even though there is no
inherent connection between the two
Bandwago
n Appeal
1
0
Red
Herring
This is a diversionary
tactic that avoids the key
issues, often by avoiding
opposing arguments
rather than addressing
them.
The level of mercury in
seafood may be unsafe,
but what will fishers do to
support their families?
The author switches the discussion away
from the safety of the food and talks
instead about an economic issue, the
livelihood of those catching fish. While
one issue may affect the other it does not
mean we should ignore possible safety
issues because of possible economic
consequences to a few individuals.
1
1
Straw Man
This move oversimplifies
an opponent's viewpoint
and then attacks that
hollow argument
People who don't support
the
proposed
state
minimum wage increase
hate the poor
the author attributes the worst possible
motive to an opponent's position. In
reality, however, the opposition
probably has more complex and
sympathetic arguments to support their
point. By not addressing those
arguments, the author is not treating the
opposition with respect or refuting their
position
1
2
Moral
Equivalenc
e
This fallacy compares
minor misdeeds with
major atrocities,
suggesting that both are
equally immoral
That parking attendant the author is comparing the relatively
who gave me a ticket is as harmless actions of a person doing their
bad as Hitler
job with the horrific actions of Hitler.
This comparison is unfair and inaccurate
EXERCISE 5
IDENTIFY THE TYPE OF FALLACIES IN THE FOLLOWING ARGUMENT
a. Red Herring
b. Ad Hominem : attacks character instead of
arguments
c. Genetic Fallacy
d. Bandwagon appeal
e. Either/Or
f. Hasty generalization
g. Mr. Lee's views on Japanese culture are wrong. This is because his parents were killed by
the Japanese army during World War II and that made him anti-Japanese all his life. Ad
Hominem
h. Smoking causes cancer because my father was a smoker and he died of lung cancer. Hasty
Generalization
i. Professor Lewis, the world authority on logic, claims that all wives cook for their husbands.
But the fact is that his own wife does not cook for him. Therefore, his claim is false. No
Fallacy
j. The last three times I have had a cold I took large doses of vitamin C. On each occasion,
the cold cleared up within a few days. So, vitamin C helped me recover from colds. Post
Hoc Ergo Propter Hoc
EXERCISE 6
Analyse the premises and the conclusion in the statements below and identify the fallacy.
1. Foreign imports are wrecking our economy and savaging our workers, the backbone of this
country. Buy Indonesian! Before you put your money on that imported fruit, think of the farmer
whose kids may not eat tomorrow.
Conclusion: Buy Indonesian!
Premise: Farmer’s kids won’t eat tomorrow.
Reasoning : Because it avoids the main issue about imports wrecking the economy and added
an irrelevant argument about how some farmer’s kid won’t eat tomorrow.
Fallacy: Red Herring
2. How can we end starvation in this world? People should eat more.
Conclusion: People should eat more.
Premise: People should eat more to end world’s starvation
Reasoning : It restates the argument by saying that to end starvation people should eat more
where the conclusion is already validated within the claim.
Fallacy: Circular argument, begging the claim
3. When he was elected President, the economy went on to grow at a record pace. He absolutely
deserves credit for it.
Conclusion: The president deserves the credit.
Premise: The economy grew at record pace when he was elected president.
Reasoning : Just because the economy grew well when he was the president, does not mean
he caused it to happen.
Fallacy: Post Hoc Ergo Propter Hoc
4. I remembered someone saying that “the strong will do what they can and the weak must
suffer”. “The powerful will do what they want, the weak must suffer”. Because of that, I assess
that the defense of Indonesia is too weak, far from what is expected.
Conclusion : Indonesia’s defense is too weak far from what is expected.
Premise: The powerful and strong will do what they want and can, the weak must suffer.
Reasoning: Concludes from insufficient proofs which are only words and not actual proofs.
Fallacy: Hasty generalization
5. We are not respected by the community of foreign reporters in Jakarta. They always say
“Indonesia is a nation of great potential and will always be a nation of great potential.” Thus,
if we want to be nice guys mediators (in addressing discrimination case in Myanmar), go ahead.
Conclusion :
Premise:
Reasoning:
Fallacy:
6. This is what we do, that is fixing the system, providing the system (online single submission)
so that the chance of committing corruption is totally gone. There is transparency in it, there is
openness in it, there is strict supervising management in it, there is good controlling
management in it.
Conclusion : Fixing and providing the system so the chance of committing corruption is gone.
Premise: There’s transparency, openness, strict supervising management and good controlling
management in it.
Reasoning:
Fallacy: