Common Mistakes in Thinking

1
Common Mistakes in Thinking

• Informal fallacy An error in reasoning
  resulting from carelessness, inattention, or
  insensitivity to language or context in which the
  argument is presented. In many instances of
  informal fallacies, we are tempted to accept the
  argument because we are not attentive enough to
  recognize that the evidential structure is
  unacceptable as presented.
• Informal fallacies are the most common kind of
  mistake in arguments. They can be hard to avoid
  or to detect precisely because they are so
  common. They are the main traps to avoid in
  arguments and scrupulously avoid in our own.

2
Ad hominem

• The first informal fallacy is the argument to the
  person. The Latin name, argumentum ad hominem,
  is probably the most commonly used of the Latin
  words in logic, and sometimes it appears simply
  as ad hominem. In this fallacy an attack is made
  on the person presenting the argument rather than
  on the argument itself. The character,
  credentials, reputation, position, or office of
  the individual is called into question instead of
  the soundness of his o her claim. The person is
  made to seem ridiculous or suspicious, and this
  is meant to undermine the argument that is
  presented.

3
Ad hominem II

• The ad hominem fallacy actually has two versions,
  personal and circumstantial. In the personal
  form (which is the most common one), the
  character or behavior of the person is
  discredited. Ad hominem almost always results
  from saying, in effect,
• So and sos claim should be rejected because
  so-and-so is ____________, where nearly any term
  with presumably negative impact is placed in the
  blank (for example, ignorant, a liar, a
  Republican, a Democrat, just saying that to
  get rich, and so on).
• Rare exceptions can occur in which a persons
  shortcomings do automatically transfer to the
  persons claim, but such a transaction takes a
  peculiar kind of circumstance. For example, He
  was paid to lie about this matter.

4
Ad hominem III

• In the 19th century the fight for Irish home rule
  was criticized because its leader, Charles
  Parnell, was an adulterer. Vincent Van Gogh
  suffered from severe depression, but that does
  not have any bearing on the aesthetic value of
  his paintings.
• The point is that in judging ideas one mustnt
  judge the person presenting the ideas. Insane
  people can write profound things, the sane can
  produce a lot of nonsense awful people can say
  good things, and saints may not be right in
  everything they argue.

5
Ad hominem IV

• In the circumstantial form of ad hominem, the
  persons position is cited as the reason to
  disregard what he or she claims. Example
• John says that we should reject what Father
  Hennesy says about the dangers of abortion
  because, After all, hes a Catholic priest, and
  priests are required to hold such views.
• It may be true that Father Hennesy is a priest
  and that is views on abortion represent those of
  the Catholic church. That does not make his
  views false, however. The specific mistake here,
  of course, is to presuppose that people always
  act for their own advantage and because of their
  position, and that does not seem fair.

6
Ad hominem V

• Ad hominem is Latin for to the man indicating
  that it is the person and not the subject matter
  thats being addressed.
• Rather than arguments ad hominem, we must use
  arguments ad rem, that is, to the thing itself.
• A variety of the fallacy of ad hominem
  circumstantial is called tu quoque or you
  yourself. Here an argument is discredited
  because the person does not practice what she
  preaches. For example, You tell me not to smoke
  but you do. Of course, if someone is seriously
  against smoking than they should not smoke.
  However, their judgment is not invalidated by the
  personal inconsistency.

7
Ad hominem VI

• This does not mean, of course, that questions
  about a persons behavior or position are always
  beside the point. If we want to know if
  candidates are fit for office, their character
  traits are certainly relevant. Such virtues as
  sincerity, fairness, integrity, and so forth are
  important considerations. However, we call it
  smear tactics when irrelevant facts about a
  persons political position or qualifications for
  public office. The fact that a woman may be
  divorced or a lesbian, for example, does not seem
  relevant to whether she would make a good
  legislator.

8
Ad hominem VII

• The argument to the person has its counterpart in
  the biographical fallacy in literature. Knowing
  that Virginia Woolf suffered from depression may
  help us interpret some of her work, but knowing
  her life has no bearing on the literary value of
  her novels.
• In other academic fields the same mistake is
  termed the genetic fallacy, and it refers to the
  attempt to explain away a claim by referring to
  the source.

9
Ad hominem VIII

• In religion, William James refers to the fallacy
  as medical materialism
• Perhaps the commonest expression of this
  assumptionis seen in those comments in which
  unsentimental people so often pass on their more
  sentimental acquaintances. Alfred believes in
  immortality so strongly because his temperament
  is so emotional. Fannys extraordinary
  conscientiousness is merely a matter of
  overinstigated nerves. Williams melancholy
  about the universe is due to bad
  digestion-probably his liver is torpid. Elizas
  delight in her church is a symptom of her
  hysterical constitution. Peter would be less
  troubled with his soul if he would take more
  exercise in the open air, etc. William James,
  Varieties of Religious Experience
• The source of an idea is irrelevant to its truth.
  

10
Argument from authority

• The argument from authority fallacy is committed
  whenever we argue for some point, not because it
  is well grounded in fact or logic but because of
  the authority of the person who presented it.
  The standing or prestige of a recognized
  authority is said to guarantee the truth of a
  claim, and anyone who doubts it is made to feel
  presumptuous or egotistical. The thrust of the
  argument is Who are you to challenge the
  judgment of this authority or the experience of
  that expert?

11
Argument from authority II

• In some ways this fallacy is the mirror image of
  the argument to the person. Rather than
  dismissing a position because of the person who
  advocates it, in the argument from authority one
  accepts a position because of the person
  advocating it. Here too the messenger is
  confused with the message. Example
• Of course different people have different
  strengths. But Aristotles definition of
  personhood emphasized rationality, so the ability
  to reason is the only personal characteristic
  that really matters.
• Cindy Crawford always drinks Pepsi. If I drink a
  lot of Pepsi, I might look like Cindy Crawford.

12
Argument from authority III

• No one can check the evidence for everything that
  is claimed, so we must depend on the information
  provided by authorities. However, and idea does
  not become true simply because an authority says
  so the person must have a good reason to say so.
  
• If we accept people as authorities it is because
  we have confidence that they support their
  insights with good thinking and good evidence.
  Furthermore, the evidence should be publicly
  verifiable, whether in the form of reproducible
  experiments or rational reasons that anyone can
  consider.

13
Argument from authority III

• A wider problem with the argument from authority
  is it suggests that an authority in one field is
  also an in another. We make this mistake very
  often in the fields of sports and entertainment.
  For instance, outstanding baseball players might
  be trusted to recommend athletic equipment but
  they are authority not qualified to endorse
  camcorders or razors in TV commercials. In the
  same way, actors are knowledgeable about acting
  but not necessarily about long distance telephone
  service, cruise lines, refrigerators, or cars.
  An ethical problem with such endorsements, of
  course is that the celebrities may not actually
  use the product they recommend but are mainly
  interested in the large endorsement fees.

14
Argument from Force

• Another informal fallacy is called the argument
  from force. This fallacy substitutes an appeal to
  motive in place of evidence in the grounds
  supporting a claim. In the appeal to force,
  someone attempts to get you to accept her claim
  because she somehow will hurt you if you do not
  agree. Example
• Your supervisor at work asks you to support her
  request for a merit raise. By all accounts,
  including your personal observation of her
  performance, she has done a thoroughly miserable
  job and does not deserve merit recognition in her
  salary. However, she makes it clear that your
  job is on the line if you do not support her. So
  you write the letter supporting her request.

15
Argument from Force II

• Arguments from force amounts to holding a gun to
  someones head and saying, I trust you will see
  the force of my argument. This device can be
  convincing, and it may ultimately prevail, but
  not because it has satisfied logical standards.
  Al Capone once remarked, You can get more with a
  kind word and a gun than you can with a kind
  word. Of course, it depends on what you are
  trying to get. You have not converted a man
  because you have silenced him. John Morley
• One may get temporary obedience through appeal to
  force but lose trust, respect, love, honest
  loyalty, and so forth.

16
Argument from Force II

• In the argument from force the intimidation
  sometimes will be overt and physical, as when
  citizens are compelled to vote for a dictator
  upon pain of death. However, usually the
  intimidation is more subtle and indirect. For
  example, if the boss strongly suggests that an
  employee agree that the safety standards are
  adequate, or that an accounting report is
  accurate, the boss is probably making an argument
  from force. The employee will feel that he or
  she had better go along, not blow the whistle, or
  else the job will go to someone who can rise
  above principles.

17
Argument from Force II

• In religious discussions people will sometimes
  say There are no atheists in foxholes, implying
  that we will always turn to religion in times of
  crisis. Even if that is true, fear is not an
  argument for Gods existence. The most famous
  example of the argument from force within
  religion is Pascals Wager.
• Pascal was a seventeenth century scientist and
  philosopher. He argued that if we believe in God
  and we are right, then we will go to heaven and
  if we believe in God and we are wrong then at
  least we will have a pleasant life on earth
  thinking that God exists and we will ultimately
  receive our heavenly reward. On the other hand,
  if we do not believe in God and we are wrong,
  then we will surely burn in hell and if we do
  not believe in God and we are right, then we will
  have a miserable life on earth, feeling that no
  divine mercy, justice or love exists.

18
Argument from Force II

• Since these are the only options, Pascal argued,
  we should certainly bet on belief in God because,
  right or wrong, we are far better off. If we
  wager on not believing then, right or wrong, we
  are bound to suffer. In essence, Pascal is
  arguing that if we know whats good for us we had
  better believe in God. Clearly the argument is
  meant to intimidate us into accepting Gods
  existence in this respect it functions as an
  argument from force. No proof is offered that
  there is a God, but only that we ought to believe
  in God to be on the safe side. However, to
  believe that something is real we need good
  reasons, not just the fear that we might be sorry
  if we didnt.

19
Appeal to pity

• Appeal to pity is a fallacy that is committed
  whenever the evidential appeal is only to the
  altruistic ideals of the hearer. Example
• Helen is running for a seat on the city council.
  Though you like her, you have doubts about her
  qualifications and in fact believe that an
  opposing candidate would make a better member of
  the council. When you communicate your concerns
  about her qualifications to a mutual friend, the
  friend counters by saying that Helen would be
  terribly hurt if she were to lose the election.
  After thinking this over, you conclude that maybe
  Helens qualifications are not so bad after all.

20
Appeal to pity II

• The mutual friend has evoked compassion in you
  for Helen, but she has not given you a reason for
  changing your opinion of Helens qualifications.
  Does your compassion for Helen enter the picture
  at all? Certainly, but only in this way You now
  have to weigh Helens hurt at losing the election
  against the consequences of having her as a
  council member instead of the BETTER QUALIFIED
  candidate. Which, you have to decide, is more
  important?

21
Appeal to pity II

• As a student you may have used the argument from
  pity at one time or another. You may have asked
  for a higher grade on an exam, arguing that you
  had studied hard but were emotionally upset or
  swamped with work. You might have said that you
  have a twenty hour a week job, your car broke
  down, you were sick with the flu, or that you are
  having trouble with your parents. Under such
  circumstances, a sympathetic professor might
  allow you additional time to do the work or even
  let you retake the exam, but if the professor
  were to raise your grade on those grounds he or
  she would not be acting in a professional way.

22
Appeal to pity III

• A higher grade would indicate that you had
  mastered the material to a greater degree than
  you actually did, thereby giving a false
  impression to anyone reading your transcript.
  Your grade should reflect your actual level of
  achievement, not how much sympathy the professor
  felt for you.
• Imagine being operated on by a doctor who never
  really mastered the skills of surgery but was
  given a passing grade by the professor how
  thought he or she deserved a break. Imagine
  driving over bridges that were designed by
  engineers who were allowed to graduate, not
  because they had met the qualifications, but
  because they had worked hard and came from poor
  families.

23
Appeal to pity IV

• Lets look at another example
• ROOFER Im positive that my work will meet your
  requirements. I really need the money, what with
  my wife being sick an all.
• The roofer seems to be giving a reason for
  thinking that his work will meet your
  requirements. But of course he is not that
  issue is unaffected by the fact that he really
  needs the money. This fact is not a reason, not
  even a bad reason, for concluding anything at all
  about the quality of his work.

24
Appeal to pity V

• Notice, though, that actions performed out of
  concern for others are often rationally and
  ethically justified. Indeed, in some instances
  they are among the noblest of human deeds. If
  the roofer is qualified and needs the money for
  his wifes illness, and you are willing to take a
  chance on him then by all means hire him! Just
  dont think that he has given you a reason for
  thinking that his work will meet your
  specifications whether it will or not is
  something you must establish on other grounds.

25
Straw Person

• Another fallacy is called straw person, the
  mistake of attributing to your opponents a
  ridiculous position that they do not hold and
  that is easily knocked down like a person made of
  straw. By exaggerating, oversimplifying, or
  distorting the other persons views, you set up
  an easy target. This absurd position, not the
  persons actual one, is then refuted by showing
  how ludicrous it is.
• The straw person device is frequently used in
  political rhetoric, functioning as a cheap way of
  winning points while evading the main issue.

26
Straw Person II

• For example, a politician might argue,
• My liberal, environmentalist friend believes in
  preserving species, that the spotted owl and the
  snail darter are more important than people. Im
  sorry, but I cannot share that view. He would
  not sacrifice a bird or a fish to safeguard a
  human being, but I would rather let an animal die
  than a person.
• Quite obviously, few if any environmentalists
  would claim that the life of a bird or fish has a
  higher value than that of a human being, but the
  environmentalists position is cast in that light
  to make it easy to refute. The environmental
  debate is not over whether we should kill people
  rather than animals but the extent to which we
  should endanger wildlife for the sake of economic
  development.

27
Straw Person III

• That, of course, is a genuine question that
  deserves to be discussed and debated. Should the
  protection of an endangered species prevent the
  development of our natural resources, especially
  if that development means increased employment,
  energy, and material products to enhance our
  lives? Are we stewards and caretakers of the
  earth, or do we have the right, perhaps the
  obligation, to exploit the earth for human
  well-being? In cases where the two are
  incompatible (as often happens in impoverished
  third world countries) which should take
  priority? These are real issues , but to frame
  the debate as a choice between killing animals or
  people is an unfair caricature.

28
Straw Person IV

• Also, cant environmentalism be compatible with
  the welfare of human beings? The world can
  survive without people, but people cannot survive
  without the world.

29
Poisoning the well

• A sister fallacy to straw person is poisoning the
  well. Here one side in an argument is placed in
  a position where it cannot refute the other
  without discrediting itself. This is done by
  making the position an undesirable one for any
  rational or decent person to hold.
• For example, a moralist might argue, Women who
  support abortion are selfish and godless people.
  They put their own needs above everything and
  everyone else, and reject the divine gift of a
  childs life. Since most women would not want
  to be regarded as selfish and godless, they might
  abandon the argument for abortion on demand.

30
Poisoning the well II

• Taking the opposite line, a feminist might argue,
  The right of a woman to have an abortion, to do
  with her body as she pleases , is opposed only by
  reactionary men who want to keep women in their
  traditional roles. Every right-thinking person
  knows this to be true. At this point any man
  who believes otherwise is reluctant to oppose
  abortion for fear of being regarded as a
  reactionary male and not a right-thinking person.
  Instances of poisoning the well happen all of
  the time in daily life. If a couple is
  quarreling the husband might say, I find you so
  defensive and your constant denials that you are
  defensive only prove my point. It is impossible
  then for the women to defend herself, since that
  would only confirm the defensiveness.

31
Poisoning the well III

• We know we are in the presence of the fallacy
  whenever we come across statements such as Any
  caring or concerned person will agree that, or
  Those who reject my solution are part of the
  problem, Only an idiot would believe
• In arguments, if we come across the ploy of
  poisoning the well we should expose it for what
  it is an attempt to place anyone who disagrees
  in an impossible position.

32
Slippery Slope

• In the slippery slope fallacy we make the mistake
  of thinking that if we take one step along a
  certain path then nothing can stop us from
  sliding inevitably to our ruin. That is, once we
  set foot on the slippery slope we are bound to
  end up in disaster. The moral, or course, is
  that we had better avoid taking that first step.
  
• Sometimes the fallacy of the slippery slope is
  described as the domino effect a slight push
  on one domino will topple the others and set a
  whole train of events in motion.

33
Slippery Slope II

• At other times it is referred to as opening the
  floodgates so that we are inundated and
  overwhelmed by the forces that we have released.
  The English often refer to the thin edge of the
  wedge, which suggests that once we allow an
  opening this will be pushed to some greater,
  undesirable result. Still other metaphors are
  we mustnt let the genii our of the bottle,
  there is a ripple effect, give them an inch
  and theyll take a mile, events can begin to
  snowball (producing an avalanche), and if the
  camel gets his nose in the tent, hell soon have
  his entire body inside.

34
Slippery Slope III

• Bureaucrats commit a common example of the
  slippery slope fallacy when they say, I would
  like to help you but if I make an exception for
  you I will have to make an exception for everyone
  else. Maybe in your situation there are
  extenuating circumstances but it is better to
  stick to the rules, otherwise everybody will
  claim they are a special case. The fallacy, of
  course, is to assume that once you initiate a
  course of action it is unstoppable. In fact,
  that is rarely true. That does not mean that
  rules are made to be broken but that it is
  possible to break rules without destroying them.

35
Slippery Slope IV

• Very few rules are without legitimate exceptions,
  so if bureaucrats insist on absolute rules, they
  are bound to commit injustices. Of course, any
  one who claims an exception has the burden of
  proof to show why the exception should be made.
• Sometimes slippery slopes do exist. Some
  developments in science and technology can be
  dangerous. When we split the atomic nucleus we
  used the energy for bombs. However, we cannot
  assume that whenever we take a first step we
  invariable lose control of events, that actions
  once unleashed must run their course and produce
  disaster. Usually we are faced with a flight of
  stairs, not a long slippery slope, and we can
  rest on any one of them.

36
Gamblers Fallacy

• The gamblers fallacy is another important
  mistake to notice because it can trap people in a
  cycle of hope and desperation. Gambling has
  become an enormous business in the United States,
  exceeding the revenues of movies, books, and
  recorded music combined. In 1993 alone gambling
  revenues exceeded 30 billion. As a result of
  gaming, Las Vegas went from a small desert town
  of three thousand people to a city of one
  million, and states are now competing with Indian
  tribes in the race to build casinos.

37
Gamblers Fallacy II

• The gamblers fallacy is one of the factors that
  keep people gambling, and it is usually described
  in terms of the maturity of the chances. A
  person playing roulette, for example, will wait
  to see which number has not come up in one
  hundred or two hundred spins of the wheel. Then
  she will bet on that number on the assumption
  that, according to statistical probability, the
  roulette ball is due to fall in that numbered
  compartment. However, at each turn of the wheel,
  each number has an equal chance of being chosen.

38
Gamblers Fallacy III

• You flip a coin ten times, and each time it comes
  up heads. But on the 11th flip, will it come up
  heads again, or tails? If you ask a random group
  of people, you will likely get two different
  answers.
• The first will be that the coin will surely come
  up heads again - it's already done so 10 times in
  a row, so the odds must be in favor of it
  happening again. The second answer will be that
  is must come up tails on the 11th flip, because
  it came up heads 10 times now and the coin is
  "due" to go the other way by now.

39
Gamblers Fallacy IV

• But both answers are wrong, and both are the
  different sides of the gambler's fallacy. Even if
  we come up with 10,000 heads in a row, the odds
  of number 10,001 being tails is still only 50/50
  (assuming that the coin is "fair", of course).
  The law of averages does not change and a random
  system does not develop a "memory." The gambler's
  fallacy represents the very real human desire to
  find some sort meaning and pattern in what
  appears to be a random system.
• As the French mathematician Joseph Bertrand
  remarked, the coin has neither memory or
  consciousness.