CS 100 - Week 9 Lecture 2 - 10-19-12
MORE fallacies of insufficient evidence (Chapter 6 continued)
loaded question
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* a LOADED QUESTION contains an UNFAIR or QUESTIONABLE
assumption;
Have you stopped cheating on exams?
Did you enjoy spoiling dinner for everyone else?
Have you finally stopped flirting with so-and-so?
(stated by your significant other)
* the point is,
there are REALLY multiple questions embedded
in these,
such that applying a SINGLE yes or no answer
to ALL of them likely results in the answerer
saying something they don't mean to;
for the 1st example above, really TWO
questions:
1. Did you cheat on exams in the past?
2. IF you did, have you stopped now?
...can't reasonably apply a single yes or no
to BOTH of these;
* (how to answer these?
DON'T let the question form dictate your answer --
DON'T preface the answer with yes or no --
instead, indicate whether you agree or disagree
with each implied characerization in succession;
QUESTIONABLE CAUSE
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* when an arguer claims, without sufficient evidence,
that one thing is the cause of something else
* three common varieties of this fallacy:
* the post hoc fallacy
* the mere correlation fallacy
* the oversimplified cause fallacy
* post-hoc variety of questionable cause fallacy:
committed when the arguer assumes, without
adequate evidence, that because A occurred BEFORE
B, A must have caused B.
I drank tea, then my cold went away -- drinking
the tea must have caused my cold to be cured!
That person moved to town, then my cow died --
that person hexed my cow to death!
* the mere correlation variety of the questionable
cause fallacy
committed when the arguer assumes, without sufficient
evidence, that because A and B REGULARLY occur
TOGETHER, then A must be the cause of B or vice versa.
Whenever I party all night and eat eggs for breakfast,
I flunk an exam I take that day.
Eating eggs for breakfast must cause me to flunk
exams.
...the problem is the mistaken assumption that
because two events occur regularly together --
because they are regularly correlated (occur together) --
that there MUST be a cause-and-effect relationship
between them;
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BUT: CORRELATION DOES NOT IMPLY CAUSATION
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* the oversimplified cause variety of the questionable
cause fallacy:
(possibly the most common form of the questionable
cause fallacy)
committed when we assume, without adequate evidence,
that A is the SOLE cause of B, when, in fact, there
are SEVERAL causes of B
Violent crime has declined steadily in recent years.
Obviously, tougher imprisonment policies are working.
...this oversimplifies by ignoring other causes that
have likely contributed to the decline --
new policing strategies, change in population,
etc.
SAT scores have fallen sharply since the 1960's.
Clearly, students are watching too much TV.
...again, an oversimplification, even if this might
be one of several possible causes; more students
take now than in the past, etc.
HASTY GENERALIZATION
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* reminder: the term generalization means a statement
that all or most things of a certain kind have a
certain quality or characteristic
all eneralds are green,
most dogs are not dangerous,
etc.
* the fallacy of HASTY generalization occurs when we
draw a GENERAL conclusion from a sample that is
BIASED or TOO SMALL
(biased, here, means a sample that is not
REPRESENTATIVE of the target/claimed population as
a whole)
Do most Americans believe X? We asked >10,000 college
students across the US, and less than 40% believed X.
The conclusion is obvious: Most Americans do not
believe X.
...but college students are not necessarily
representative of the entire American population;
I've hired 3 people-of-X in the past 6 months.
All 3 were [undesirable in some way]. So, all
people-of-X must be [undesirable in some way].
...that's too small a sample;
SLIPPERY SLOPE
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* committed when we claim, without sufficient evidence,
that a seemingly harmless action, if taken,
will lead to a disastrous outcome
* We can't allow A, because A will lead to B,
and B will lead to C, and we sure as heck
don't want C!
WEAK ANALOGY
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* occurs (as a fallacy) when an arguer compares two or
more things that aren't really comparable in
relevant respects (relevant to the conclusion, that is)
lettuce is leafy and green and great on a burger!
poison ivy is also leafy and green!
...so it also must be great on a burger!
3 common patterns:
* 2 things with several identified similarities
(as above)
* several things but only 1 or 2 identied similarities
* simply to assert, WITHOUT further elaboration,
that 2 cases are relevantly similar
...more on this on Tuesday!