Homework

1
(No Transcript)
2
Homework

• Study Fallacies 1-18
• Review pp. 103-137
• Fallacies (definition)
• 3.1 Fallacies of Relevance (1 7)
• 3.2 Fallacies of Weak Induction (8 14)
• For Next Class pp. 137-144
• Fallacies of Presumption (15 18)

• Study Tip
• How is each fallacy a fallacy of that type?
• e.g. how is the fallacy of weak analogy a
  fallacy of weak induction?
• e.g. how is begging the question a fallacy of
  presumption?

3
Informal Fallacies
4
Kinds of Informal Fallacies

• Fallacies of
• Relevance
• Weak Induction
• Presumption
• Ambiguity or Whole/Part

See pages 151-52 for a complete list
5
Fallacies of Weak Induction
6
Weak Induction

• Premises are relevant to conclusion
• Insufficient evidence to warrant conclusion

7
The Five Fallacies of Weak Induction

• Appeal to Ignorance
• Appeal to Unqualified Authority
• Hasty Generalization
• False Cause
• Weak Analogy

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

8
The Five Fallacies of Weak Induction

• Appeal to Ignorance
• Smoking has not been proven to cause cancer,
  therefore tobacco products are not carcinogenic
• Premises offer only a lack of evidence
• A definite assertion is made on this basis

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

9
The Five Fallacies of Weak Induction

• Appeal to Ignorance
• Smoking has not been proven to cause cancer,
  therefore tobacco products are not carcinogenic
• Exceptions (see text)
• If search for evidence has been (seemingly)
  exhaustive by qualified personnel
• American Legal Standard reasonable doubt

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

10
The Five Fallacies of Weak Induction

• Appeal to Unqualified Authority
• I was speaking to my brother at his shop as he
  was fixing my car, and he believes the Obama
  financial plan will produce enormous inflation.
• Premises offer testimony/opinion from an
  authority
• Not a credible or qualified authority on subject
  matter
• A conclusion about subject matter is made on this
  basis

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

11
The Five Fallacies of Weak Induction

• Hasty Generalization
• Issues affecting strength of generalization
• Sample size
• A function of representativeness
• Sample not randomly selected
• Interviewer bias (in surveys)

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

12
The Five Fallacies of Weak Induction
Sample not randomly selected

• Hasty Generalization
• Kentucky Secretary of State Trey Grayson
  predicted about 42 percent of the voters in
  Kentucky will cast ballots. Kentucky has 2.8
  million registered voters, including about 1.6
  million Democrats, about 1 million Republicans
  and 186,451 people registered as "other."
  Grayson, Kentucky's top election official, said
  the projection was based in part on an increase
  in absentee ballots cast in the days before
  Tuesday's election. The number was up by about 20
  percent from the 2003 election.

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

13
The Five Fallacies of Weak Induction
Size unknown in relation to population

• Hasty Generalization
• Kentucky Secretary of State Trey Grayson
  predicted about 42 percent of the voters in
  Kentucky will cast ballots. Kentucky has 2.8
  million registered voters, including about 1.6
  million Democrats, about 1 million Republicans
  and 186,451 people registered as "other."
  Grayson, Kentucky's top election official, said
  the projection was based in part on an increase
  in absentee ballots cast in the days before
  Tuesday's election. The number was up by about 20
  percent from the 2003 election.

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

14
The Five Fallacies of Weak Induction

• False Cause
• Four variants (complex fallacy)
• Post hoc ergo propter hoc (after this, therefore
  because of this)
• Non causa pro causa (non-cause for the cause)
• Oversimplified cause
• Slippery Slope

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

15
The Five Fallacies of Weak Induction

• False Cause
• Your car is causing global warming.
• Phenomenon in question caused by complex number
  of factors
• A single one of these factors is asserted as sole
  cause

oversimplification

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

16
The Five Fallacies of Weak Induction

• False Cause
• If you fail this class, then your GPA will go
  down. If you GPA falls, youll lose your
  scholarship. If you lose your scholarship,
  youll spend all your money on school. If you do
  this, youll have no money for food and shelter.
  So if you fail this class, you will become a
  starving, homeless beggar.
• A chain of causal events is asserted
• The causal connection between some or all events
  is highly unlikely
• At least the ultimate conclusion is highly
  unlikely

slippery slope

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

17
The Five Fallacies of Weak Induction

• Weak Analogy
• Factors affecting strength
• Relevance of commonalities to inferred feature
• Number (extent) of these similarities
• Diversity among common features
• Number of analogues
• No relevant dissimilarities (disanalogy)

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

18
The Five Fallacies of Weak Induction

• Weak Analogy
• Chimpanzees and humans are genetically almost
  identical. There is only a very small number of
  genetic markers which differ between the two
  species. Chimpanzees are good climbers. Hence
  humans are also likely good climbers.
• Relevant dissimilarity, since chimps are much
  stronger than humans

• In each case,
• The premises are relevant to conclusion
• Premises provide insufficient evidence to warrant
  conclusion

19
Comparable Entities?
Dog?
My dog
20
Fallacies (on exam)

• (i) Identify the fallacy or fallacies committed
  in each of the following arguments. (ii) Explain
  clearly how this argument is fallacious. If you
  believe no fallacy is committed, explain this
  choice. (Each question is worth 10 points)
• Identify
• Explanation

• fallacy of relevance
• fallacy of weak induction
• fallacy of presumption
• fallacy of ambiguity or whole/part
• none of the above

See pages 151-52 for a complete list
21
Fallacies of Relevance
22
Relevance vs. Weak Induction

• Fallacies of Relevance
• Premises are logically immaterial to conclusion
• Typical features
• tactic of distraction
• conclusion rests on emotional appeal
• Premises may appear to be psychologically
  relevant
• Fallacies of Weak Induction
• Premises are relevant to conclusion
• Insufficient evidence to warrant conclusion

23
Fallacies of Relevance

• Appeal to Force
• Appeal to Pity
• Appeal to the People
• Direct
• Indirect
• Argument against the Person
• Abusive
• Circumstantial
• You, too!
• Missing the Point
• Of Accident
• Straw Man
• Red Herring

• Latin vs. English names
• Ad baculum
• Ad misericordiam
• Ad populum
• Ad hominem
• Ignoratio elenchi

24
Fallacies of Relevance

• Appeal to Force
• Appeal to Pity
• Appeal to the People
• Direct
• Indirect
• Argument against the Person
• Abusive
• Circumstantial
• You, too!
• Missing the Point
• Of Accident
• Straw Man
• Red Herring

• Latin vs. English names
• Ad baculum
• Ad misericordiam
• Ad populum
• Ad hominem
• Ignoratio elenchi

25
Fallacies of Relevance

• Appeal to the People
• Two Kinds
• Direct Approach
• Appeal to group
• Appeal to emotions, either positive or negative
• Evidence overlooked due to cloud of emotional
  attachment
• Demagoguery
• Indirect Approach
• Appeal to individuals
• Appeal to attachment or relationship to crowd
• Evidence overlooked in favor of emotional
  attachment

26
Fallacies of Relevance

• Example appeal to the people?
• " The most talked-about aspect of the defense
  case undoubtedly concerned Mark Fuhrman, the LAPD
  officer who had found the bloody glove and who,
  as a prosecution witness, denied using the word
  "nigger." It turned out that Fuhrman had used
  "the n word"--many times--and it was on tape.
  Laura Hart McKinny, an aspiring screenwriter from
  North Carolina, had hired Fuhrman to consult with
  her on police issues for a script she was
  writing. McKinny taped her interviews with
  Fuhrman, who not only used the offensive racial
  slur, but disclosed that he had sometimes planted
  evidence to help secure convictions. Needless to
  say, the defense wanted McKinny on the stand, and
  they wanted the jury to hear selected portions of
  her tapes. The prosecution strenuously objected,
  arguing that McKinny's testimony was irrelevant
  absent some plausible evidence suggesting that
  evidence was planted in the Simpson case. The
  prejudicial value of the testimony, the
  prosecution insisted, would exceed its probative
  value.

The Trial of O.J. Simpson by Doug Linder
27
Fallacies of Relevance

• Ad Hominem Arguments (against the person)
• Three varieties
• Abusive attack on character of arguer
• Turn attention away from the argument to the
  arguer
• Circumstantial attack by reference to specific
  irrelevant circumstances affecting arguer
• Evidence for proposed conclusions overlooked in
  such attacks
• You, too! attack by charge of hypocrisy
• Irrelevant behavior characteristics overshadow
  argument

28
Fallacies of Relevance

• Examples attack against the person?
• Prof. Smith says to Prof. White, "You are much
  too hard on your students," and Prof. White
  replies, "But certainly you are not the one to
  say so. Just last week I heard several of your
  students complaining."

29
Fallacies of Relevance

• Straw Man
• Someone misrepresents anothers argument
• Presents weaker argument
• Straw man vs. real man
• Attacks weaker argument as if it were the
  original
• Distorted argument often a fabrication

30
Fallacies of Relevance

• Example straw man?
• Darwin's theory of evolution asserts that human
  beings developed after a long process of change,
  from pre-hominid ancestors who are also the
  source for our primate relatives - chimpanzees,
  gorillas, etc. If Darwin's theory is correct,
  then we can no longer assert with such arrogance
  that we are above the animals rather, human
  beings and human intelligence are simply
  different, but related results of the same
  evolutionary process that has produced the rest
  of the animal kingdom.

Not Fallacious
31
Fallacies of Relevance

• Red Herring (stinky fish)
• Someone diverts attention from subject at hand
• Introduction of a controversial, hot-button issue
• The original argument tied illegitimately to
  controversial position (the stinky fish)
• Controversial position attacked for its
  outlandishness

32
Fallacies of Relevance

• Example red herring?
• Appearing on ABC's This Week, the Ohio Republican
  (Minority Leader John Boehner) was asked what to
  describe the GOP plan to dealing with greenhouse
  gas emissions, "which every major scientific
  organization said is contributing to climate
  change."
• Boehner replied "The idea that carbon dioxide is
  a carcinogen that is harmful to our environment
  is almost comical. Every time we exhale, we
  exhale carbon dioxide. Every cow in the world,
  you know when they do what they do you've got
  more carbon dioxide."
• "It's clear we've had change in our climate," he
  added. "The question is how much does man have to
  do with it and what is the proper way to deal
  with this? We can't do it alone as one nation."

The Huffington Post, Boehmer Cites Cow Farts to
Downplay Global Warming
33
Fallacies of Relevance

• Appeal to Force
• Appeal to Pity
• Appeal to the People
• Direct
• Indirect
• Argument against the Person
• Abusive
• Circumstantial
• You, too!
• Missing the Point
• Of Accident
• Straw Man
• Red Herring

• In each case, attention is drawn away from
  supporting evidence
• appeal to some irrelevant concern
• often intentionally deceptive