Text Table of Contents #11:
How Good is the Evidence? Rival Causes
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Ambiguities
◦ Why is identifying them important?
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Faithfulness and Charity in analyzing an
argument.
◦ Context is important in interpreting what the author is
communicating.
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Evaluating the argument / reasons: use caution
◦ Usually will NOT “Fail” a reason outright.
◦ Usually we will decide on a level of “confidence” in the
reason – a degree of probability / acceptance.
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Truth – is it true (by common knowledge) or at least probably true?
◦ For example, as we have to assume more things to accept a reason as true – the
likelihood of the reason being acceptable decreases.
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Logical strength – if the reason is true could we conclude otherwise?
◦ Could these reasons lead to a different conclusion?
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Relevance – do we need the reason for the conclusion to be true?
◦ Could different reasons lead to this conclusion?
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Circularity – does the conclusion assume or include the reason(s)?
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ConcL: I have earned an A in this class.
R1: I have attended every class and
completed every assignment and exam.
R2: I have put in more effort than in any other
class this semester.
R3: I have an A average for all criteria on the
syllabus including assignments and exams.
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I like all democrats
Obama is a democrat
Therefore I like Obama
What is the relative degree of relevance of the reasons to the
conclusion?
◦ If there was only one other reason I could like Obama – for
example I might like him because he takes the same position as
I do on something important?
◦ If there were 10 other reasons I might like Obama like his
youth, his integrity, his voting record, etc.?
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Circularity?
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Rival Cause:
◦ A plausible alternative explanation for why an outcome
occurred.
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Applies to:
◦ Reasons related to the conclusion
◦ Evidence / supporting reasons related to main reason.
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Ex: muffler problem
◦ concluded vibration caused by broken baffles
◦ but could have been caused by loose bracket, etc.
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Oversimplification: in many situations there
are complicated causal relationships.
Research – difficult to account for all
differences between the groups studied.
Causation vs. correlation.
When you identify possible alternative causes
test them for logical strength and probability.
Ex: Researchers identify alternates in order to
support their own conclusions.
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Form groups of 4-5, take out paper and write
down all members’ names.
Gun control is like trying to reduce drunk
driving by making it tougher for sober people
to own cars.
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Gun control is like trying to reduce drunk driving
by making it tougher for sober people to own
cars.
Gun control as typically discussed makes owning
◦ some weapons impossible (like assault rifles) for all
people
◦ all weapons hard or impossible for some people (like
crazy people or felons).
◦ Does affect non-criminals - for some weapons.
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I was recently hired to find the best cherry pie
recipe in the state of Virginia. I found it in the
kitchen of Evelyn Smith. My search began by
requesting all interested cherry pie tasters to
answer my newspaper ad. All respondents in
the state met in a central location and tasted
cherry pies. Each of 68 persons tasted the five
cherry pies that were judged superior at the
recent Virginia State Fair. To assure fairness,
each "taste" was made on a different day so that
the taste buds would not be confused. The
winner? Ms. Smith’s pie! She received over 40
percent of the votes. Her closest competitor
received 22 percent. Apparently, Ms. Smith has
something special when it comes to cherry pies.
According to a recent study, one of the major
causes of violence in schools is listening to
aggressive heavy metal music. Researchers
studied more than 100 cases of “serious”
violence within schools and found that 68% of
the children involved in the violence listened to
heavy metal music. These children would
frequently come to school with headphones,
listening to this music, as well as wearing
clothing from heavy metal bands. Frequently,
these heavy metal songs discuss violence, and
therefore are a direct cause of school violence.