Text Table of Contents #5 and #8:
Evaluating the Argument
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Arguments intend to convince us to accept a
conclusion – i.e., a position, claim, belief, etc.
Why does the author want us to accept this
conclusion?
The reasons tell us why that conclusion should
be accepted.
Accepting the conclusion based on the reasons
is reasoning.
But there are some presumptions we need to
make in order to accept the reasoning.
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Are the reasons true?
Is the logical connection between the
reason and conclusion strong?
◦ The conclusion must be true or probably true if the reason
is true.
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Are the reasons relevant to the conclusion?
◦ Truth of conclusion depends on the reason.
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Circularity - the reason can’t depend on the
conclusion
◦ Can’t say “the reason because of the conclusion.”
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Infer  deduce or conclude (information) from evidence and
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Strength of Logic = Validity of Inference
reasoning rather than from explicit statements (Oxford dictionary)
◦ does not refer to truth of premise or conclusion
◦ refers to the form of the inference
◦ i.e., how the inference is drawn
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A word about inference - induction vs. deduction
 induction – results in probable conclusion
 deduction results in certain conclusion
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All fruits are sweet.
A banana is a fruit.
Therefore, a banana is sweet.
For the conclusion to be necessarily true, the
premises need to be true.
Strong Logic
◦ The conclusion is true or probable if the reasons
are true.
◦ Ask yourself: Could the conclusion be wrong if the
reasons are true?
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R1. When a muffler gets old the baffles loosen.
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R2. Loose muffler baffles often rattle when idling.
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R3. My muffler is old.
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R4. A rattling noise is coming from underneath my
car in the back or middle area when idling.
Conclusion:
◦ The rattling sound is coming from my muffler.
◦ Could the rattling not be coming from the muffler even if
the reasons are all true?
◦ Could anything else be explained by the reasons?
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State data show that average state funding for
colleges has shrunk by 20-30% in the last five
years.
Based on recent alcohol industry data, selling
alcohol on campus has increased revenues by
several percentage points for colleges that permit
on-campus alcoholic beverage consumption.
Conclusion:
◦ Colleges can offset reduced state funding by permitting
alcohol consumption in college-operated on-campus
venues.
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Leading from true premises to a false
conclusion.
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All apples are fruit. (correct)
Bananas are fruit. (correct)
Therefore, bananas are apples. (incorrect)
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Weak Logic
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◦ The reasons are true
◦ But the conclusion does not follow
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Students who served in the military deserve a
beer.
It (alcohol consumption on campus) will create
a more diverse environment on campus.
Conclusion:
◦ College students should be able to consume liquor.
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Logical strength is:
◦ Does the conclusion have to be true (or probable) if
the reason(s) is(are) true?
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Relevance is:
◦ Do the reasons have to be true for the conclusion to
be true?
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In the muffler example assume that the car
has nothing else in the area described that
could come loose and rattle.
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R1. When a muffler gets old the baffles loosen.
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R2. Loose muffler baffles often rattle when idling.
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R3. My muffler is old.
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R4. A rattling noise is coming from underneath my car
in the back or middle area when idling.
Conclusion:
◦ The rattling sound is coming from my muffler.
◦ Could the muffler be rattling and it not be broken baffles?
◦ Got the right conclusion – but has nothing to do with reasons.
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When the conclusion serves to support a reason.
◦ Typically the conclusion is contained in a single assumption.
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Most obvious circularity when the conclusion is simply
another way of stating (or very similar to) the reason.
◦ Concl: You can’t give me a C.
◦ R1. I am an A student.
 Another way of stating the argument is: You can’t give me a C
because I am not a C student.
◦ Concl: Stealing is wrong.
◦ R1. There is a law against stealing.
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Something is illegal because it’s “wrong” to do it.
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Is the reason true?
◦ Do I have have to assume anything to accept the reason?
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Is the reasoning logically strong?
◦ Could the conclusion be unlikely if the reason is true?
◦ Could a different conclusion be true due to the reason?
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Is the reason relevant to the conclusion?
◦ Does the reason have to be true for the conclusion to be true?
◦ Could the conclusion be true due to some other reason?
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Is there any circularity in the reasoning?
◦ Do the reason and conclusion assume each other?
◦ Do the conclusion and reason seem to be the same or similar?
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Assumptions are a key issue.
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Assumptions are key – there is a potential
problem in the reasoning / logic (fallacy) if:
◦ A reason is an assumption – i.e., it does not refer to any
data, facts, or evidence (truth).
◦ A reason requires an assumption to connect it to the
conclusion (relevance).
◦ A reason assumes or depends on the conclusion
(circularity).
◦ The conclusion requires an assumption not stated in a
reason to be accepted (relevance).
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According to ARQ - most fallacies in the reason
or reasoning relate to:
◦ Mistakes or problems with assumptions required (truth
and /or relevance).
◦ Distractions from the reason or conclusion (relevance).
distractions often require making inappropriate
assumptions to link to conclusion.
Reasons depending on conclusion being true (circularity).
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Ad hominem – attack on person not reason
(relevance).
Slippery slope – assuming conclusion applies to
other un-related situations (relevance).
Appeal to emotions – using “loaded’ terms to
frame a reason or position (relevance).
Appeal to popularity – if a group of people accept
it everyone should (relevance).
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Fallacies in commercials and pop culture
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False Dilemma
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A short animation of some fallacies.
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Appeal to authority – citing an authority without
evidence of authority’s expertise related to the
issue (relevance).
Word play or equivocation – intentionally use
ambiguity to support reason (relevance).
Appeal to ignorance – absence of reason for
something is proof against it (relevance).
Appeal to perfect solution – attack conclusion for
not solving all problems.
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Glittering generalities - using ambiguous but
“positive” terms to get acceptance.
Straw-man – distorting or misstating a point
to attack a point that doesn’t exist.
Red herring – diverting attention to a nonrelated topic.
Explain by naming – naming it doesn’t
explain it.
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Identify issue, conclusion, reasons.
Does conclusion identify a specific / concrete advantage
or disadvantage ?
For each reason ask:
◦ What do I have to believe / assume to accept it as true?
◦ What do I have to believe for it to support conclusion?
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Do these beliefs / assumptions make sense - are they
reasonable?
Have any of the reasons distracted me from the relevant
reasons by appealing to emotions?
What made Harry Needamore, the chief
executive of Slippery Oil, so obsessed with
making money that he was willing to mislead
investors and falsify accounting information
such that his deception cost innocent investors
millions of dollars? He is a psychopathic
personality. It seems that all such extreme cases
of corporate fraud come from this cause, as Mr.
Needamore’s case so clearly demonstrates.