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An argument is
a line of reasoning designed to prove a point. Arguments can be
simple, expressed in a few lines, or very complex, taking up whole books.
Regardless of length and complexity, all arguments have the same basic
framework: the author states some central idea, and then presents supporting
evidence, laying it out in a logical pattern.
The central point
of an argument is called the conclusion. Each piece of evidence
used by the author is called a premise. And the way in which the
premises are combined is called reasoning.
Premise:
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All birds fly.
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Premise:
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Penguins are birds.
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Conclusion:
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Penguins fly.
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The above example presents a simple argument. The conclusion
is based on two premises. The argument is valid - if the premises
are true, the conclusion must be true. It is an unsound argument,
however, since the first premise is false.
Note that a premise
does not have to contain objective, factual evidence to support the conclusion.
In fact, a premise does not even have to be true. A premise is
any statement that the author uses to support the conclusion.
To identify the
conclusion of an argument, ask yourself what central point the author
is trying to make. What is the author trying to prove? Think
about the one idea the author would want you to take away after reading
the argument. That idea is the conclusion of the argument.
When you are writing, question whether it will be clear to your reader
what exactly your conclusion is. Is your reader going to be able
to easily distinguish between your premises and your conclusion?
Certain structural
words can help you indicate your conclusion. Use words such as:
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therefore
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thus
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hence
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consequently
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accordingly
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so
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as a result
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it follows
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suggests
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indicates
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The premises of an
argument are statements made by the author to support the conclusion.
Structural words that indicate a premise include the following:
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since...
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because
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for
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inasmuch as
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insofar as
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due to
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Consider the following
and identify the conclusion and the premises.
Dogs make better pets than do cats. Dogs provide companionship
and protection, whereas cats are more aloof and do not guard against
intruders.
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Note that the
actual sequence is not important: the logic of the argument is the same
whether the conclusion follows the premises or precedes them.
Assumptions
In an argument, an assumption is a premise that is not explicitly (directly)
stated. These unstated premises are very important since the validity
of an argument is determined by the validity of its assumptions.
Assumptions are
the missing links of arguments. You can think about assumptions
in visual terms. Imagine the premises of an argument as spans of
a bridge leading to the conclusion. An assumption - an unstated
premise- is a missing span. The author takes for granted that it
is there, but we cannot see it. Many students however, err by making
too many assumptions, their whole bridge is made up of missing spans.
Example:
Senator Franklin is a member of the Orange Party, which supports
increased military spending by Federal government. Franklin will
surely vote for a cut in spending on social programs.
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The argument
assumes which of the following?
A
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Elected officials always support policies endorsed by their parties.
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B
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The only way to increase military spending by Federal government
is to
cut spending on social programs.
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C
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Senator Franklin agrees with the policies of his party.
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D
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The orange Party has the majority in the senate.
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E
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Senator Franklin opposed Federal spending on social programs.
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What is
the underlying assumption in the example? Note that what we are
interested in is the major assumption in the argument - the unstated premise
without which the argument would not work.
To make
it easier to see how the author proceeds from the premises to the conclusion
and to see which premise is not explicitly stated, we can rewrite the argument
as follows, clearly identifying the premises and the conclusion:
Premise:
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The Orange party supports increased military spending by the Federal
Government
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Premise:
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Senator Franklin is a member of the Orange Party
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Conclusion:
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Senator Franklin will vote for a cut in spending on social programs.
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It is evident
that the conclusion does not follow from the premises. In order
for this argument to work, there must be another premise, which is assumed
by the author. The most important missing link here is the connection
between increased military spending by the Federal government and a reduction
in spending on social programs. If we insert a premise that connects
the two, the argument works.
Premise:
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Senator Franklin is a member of the Orange Party
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Premise:
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The Orange party supports increased military spending by the Federal
Government
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Assumption:
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The only way to increase military spending by the Federal government
is to cut spending on social programs.
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Conclusion:
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Senator Franklin will vote for a cut in spending on social programs.
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Note: It is the writer's responsibility to make himself understood.
Don’t make too many assumptions and rather than omit - include as many
premises as are necessary to make your argument clear. Different
readers may not recognise or indeed may make false assumptions so if you
want to be understood, state everything clearly.
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The validity
of the major assumption made in an argument largely determines whether
that argument is logical. Therefore, a statement that strengthens an
argument supports its major assumption. On the other hand, a statement
that weakens an argument undermines its major assumption.
Example
Some scientists have argued that the effect of dust storms on the
surface temperature of Mars reliably predicts a ‘nuclear winter’ on Earth
following a nuclear war that would stir up a comparable amount of debris.
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Which
of the following, if true, would tend to most weaken the argument predicting
a ‘nuclear winter’?
A
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A nuclear war is unlikely because all participants would suffer almost
total annihilation.
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B
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The chances of a nuclear war occurring are likely to decrease as
a result of disarmament.
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C
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People could survive a ‘nuclear winter’ if they were adequately
prepared.
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D
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There is no evidence of life on Mars.
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E
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There is no water in the atmosphere of Mars, and therefore the effect
of dust on surface temperature is not comparable to the corresponding
effect on Earth.
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Example
The rate of violent crime has risen over the last ten years.
Some sociologists insist that violence depicted on television is responsible
for this trend.
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Which of the following, if true, would most strengthen the argument?
A
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Violent criminals have more psychological problems than criminals
who are not violent.
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B
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Guns are used more than any other weapons in violent crimes.
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C
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The stringent rules that regulated the content of television programming
were greatly eased 15 years ago, resulting in widespread depictions of
graphic violence.
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D
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The overcrowding of prisons has resulted in reduced terms for many
criminals.
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E
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Violent criminals are much more prone to suggestion than people who
do not commit crimes.
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Methods of Argument
Deductive
Arguments
Deductive arguments are designed to prove definitively the author’s conclusion.
In a deductive argument, the conclusion necessarily follows from the
premises. If the premises are true, the conclusion must be true.
Deductive arguments use generalizations as premises to proves specific
conclusions.
Premise:
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All children like chocolate
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Conclusion:
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My nephew Nick, who is 4 yrs old, must like chocolate.
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The example above is a valid deductive argument. The conclusion
follows necessarily from the premise. The argument is valid but
untrue- it is unsound because the premise is false.
Inductive
Arguments
Inductive arguments use limited specific experience to support the probability
of a generalized conclusion. In an inductive argument, if the premises
are true, the conclusion is probably true.
Premise:
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Tom’s stereo has worked every time he has used it.
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Conclusion:
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Tom’s stereo will work today.
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In this example, the conclusion does not follow from the premise.
The argument is a relatively strong one, however, since the conclusion
is probably true if the premise is true.
Causal Arguments
Causal arguments usually appear in explanations. An example of a
causal argument is a scientific hypothesis that explains a natural event
e.g.. lower global temperatures result from increased volcanic activity.
Quite often causal arguments confuse correlation - coincidental occurrence-and
causality. Do not assume that if X happened right before Y, X caused
Y. Always consider alternative causes.
Statistical
Arguments
Statistical arguments use statistics in their premises.
Premise:
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Four out of five dentists recommend Superdent toothpaste to their
patients.
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Conclusion:
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Use Superdent.
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Statistical arguments are often invalid because they use samples that
are too small or are not representative of the group the conclusion focuses
on. Be especially wary of arguments that make conclusions about the
whole based on the attributes of its parts, or vice versa.
Analogous
Arguments
Analogous arguments use analogies in their premises.
Premise:
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Broccoli has been shown to be very beneficial to one’s health.
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Conclusion:
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Spinach must also be good for you.
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The strength of analogous arguments depends on the similarity between
the elements of their analogies. These arguments can never prove
their conclusions, they can only support them.
Useful
links
A Glossary of terms used when discussing arguments
Sample Arguments
Examples
of things Students say but probably don't mean
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