Logical Fallacies

1
Logical Fallacies

• Dr. Alan Haffa
• Based on Gary Goshgarian and Kathleen Krueger in
  An Argument Rhetoric and Reader

2
What Are Logical Fallacies?

• Fallere to deceive
• Flaw in the logic of an argument
• Unintentional or inteional

3
Ad Hominem

• Attack against the man
• Attacks the character or person of the person
  making the opposing argument rather than the
  argument itself
• Shows lack of objectivity

4
Ad Misericordiam

• Appeal to Pity
• Attempts to persuade by making an emotional
  argument
• Example Local Humane Society seeks money for new
  shelter shows a picture and tells you that your
  donation could save this dog from being
  euthanized due to overcrowding
• Appeal to a court to spare an eighty year old man
  from the death penalty based upon his age and
  frail health

5
Ad Populum Argument

• An argument aimed at appealing to the prejudices
  and emotions of the masses
• A parent who complains in an editorial about
  their child being taught by a foreign teacher,
  appeals to the common prejudice against
  immigrants and foreigners
• Just because a majority believe something is true
  doesnt make it logical or valid

6
Bandwagon Appeal

• If you dont want to be left out, you better get
  on the bandwagon and do and think the same things
• Similar to Ad Populum but emphasis is on the
  desire to persaude the undecided or
  non-conformist to join the group
• Smart Shoppers shop at Sears
• Everyone knows that Global Warming is a Threat
  Everyone knows that Global Warming is a liberal
  conspiracy

7
Begging the Question

• Similar to circular reasoning, begging the
  question presents something as true which in fact
  needs to be demonstrated.
• That foolish law should be repealed
• She is compassionate because she is a woman

8
Circular Reasoning

• The conclusion of a deductive argument is hidden
  in the premise
• The argument goes in a circle
• 1) People who are happy with their work are
  cheerful because they enjoy what theyre doing
• Smoking is bad for you because it ruins your
  health.

9
Dicto Simpliciter

• From a general truth to a specific case,
  regardless of the appropriateness
• Simply spoken
• Exploits an overly simplistic rule of thumb
• 1) Men are stronger than women Soldiers should
  be strong Women should not serve in combat.

10
False Analogy

• Analogy compares two things
• False analogy is when the two things compared
  really are not similar in the way being compared
• Sadaam Hussein is like Hitler
• Therefore, the Gulf War is justified just as WW
  II was justified

11
Faulty Use of Authority

• When an expert in one area is used as an
  authority outside of their area of expertise
• Just because someone is a Ph.D. or M.D. doesnt
  mean that they are an expert on the particular
  topic
• Celebrity Endorsements

12
Hasty Generalizations

• Arriving at a conclusion based on too little
  evidence
• Students in America are learning less than in the
  past because their SAT scores are lower
• California students are less well educated than
  other states because they are 44th in per student
  funding

13
Non Sequitur

• Does not follow
• A conclusion that doesnt follow from the premise
• Shes so pretty she must not be smart.
• Candidate Jones will be a great Senator because
  shes been married for twenty years.

14
Post Hod, Ergo Propter Hoc

• After this, therefore because of this
• Establishes a questionable cause-and-effect
  relationship between events
• Because event Y follows event X, event X causes
  event Y
• Black folks do less well on standardized tests
  therefore the public school system must be racist
• There are more latch-key children since the
  Womens Movement Feminism and Womens Liberation
  is directly responsible for the rise of latch-key
  children

15
Red Herring

• Evidence that is used incorrectly and
  intentionally to distract the audience from the
  true issues
• In Detective Stories the Red Herring is the
  false suspect
• A coach accused of using money improperly defends
  himself by pointing out the teams winning record
• The problem with education is a lack of
  accountability

16
Slippery Slope

• Like a muddy hill, if we go down this slope we
  will fall
• In other words, if we allow one thing a whole
  slew of other, negative events will occur as a
  result
• Domino-effect
• It is fallacious when there is not sufficient
  evidence offered to show that Event X will
  necessarily lead to Events Y and Z
• If Gay marriage is allowed, group marriage,
  incest, and bestiality will soon follow

17
Stacking the Deck

• Only offering evidence that supports the premise,
  while disregarding contrary evidence
• Data beautification
• A meat manufacturer advertises that its all-beef
  hot dogs now contain 10 percent less fat, but
  leaves out the fact that it still contains 30
  fat
• If you leave out obvious evidence your reader
  knows about you lose credibility

18
Straw Man

• A straw man is an easy target
• In rhetoric, it refers to a strategy of
  refutation that offers a distorted view of the
  opponents position and then knocking it down.
• The speaker claims the opponents argument is
  false because of an error in a smaller,
  inessential part of the opponents argument
• Senator X claims that we should not spend money
  on the superbomber program. Do we really want her
  to leave our country defenseless?

19
Summary

• If you can identify a fallacy in your opponents
  argument, point it out and show how it is false
• Be sure to refute all of your opponents points
  and then you may offer up points of your own.