LOGIC AND CRITICAL THINKING by Karey Perkins

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LOGIC AND CRITICAL THINKINGby Karey Perkins
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RHETORICAL APPEALS USING LOGOS, ETHOS, PATHOS

• LOGOS LOGIC and REASON Soundness of facts,
  evidence, statistics, and reasoning soundness of
  authoritys statements outside self
  well-documented evidence
• ETHOS Credibility and reliability of writer
  him/herself character and reputation of the
  author
• PATHOS EMOTION Appeal to needs, values, and
  attitudes uses the emotional power of language

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??

• ACME's new dihydro-cesium detonation process
• By combining cesium and dihydro-oxide in
  laboratory conditions, and capturing the released
  energy, ACME has promised to lead the way into
  the future. Our energy source is clean, safe,
  and powerful, according to laboratory tests. In
  20 tests conducted over a period of 5 years, no
  pollutants were released into the atmosphere.
  The world will soon have an excellent source of
  clean energy. ACME is currently working toward a
  patent on our process. Our scientists are
  exploring ways to use the process in cars,
  houses, airplanes, and almost anything else that
  needs power. ACME batteries will be refitted with
  small dihydro-cesium reactors. Once the entire
  world is powered by ACMEs generators, we can all
  relax and enjoy a much easier life.

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• Acme Gizmotronics, the company that you've
  trusted for over 100 years, has recently entered
  the World Wide Web! Now you can purchase our fine
  products through the Internet. Our quality
  gizmos, widgets, and thingamabobs can be shipped
  to you within minutes. All come with the famous
  lifetime guarantee that makes Acme the company
  that the world depends on for its gizmo needs.

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• CESIUM-BASED REACTOR KILLS!
• A baby turtle breaks free from the leathery
  shell of its egg, catching its first glimpse of
  its first sunrise. It pauses a moment to rest,
  unaware of the danger that lies so close to it.
  As the tide comes in, approaching the nest, it
  also approaches a small pile of metal cesium.
  The water draws closer and closer, the turtle
  unsuspecting of the danger. Finally, the water
  touches the cesium.
• The nest is torn to bits in the resulting
  explosion, destroying even more of an endangered
  species.
• Why does this happen? One name Acme.
• (Examples from The Art of Rhetoric
  Learning How to Use the Three Main Rhetorical
  Styles. Available at (http//www.rpi.edu/dept/l
  lc/webclass/web/project1/group4/ ))

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SUCCESSFUL ARGUMENTSpersuade the reader by means
of

• Clear premises and conclusions
• Evidence, not unsupported claims and appeals to
  emotions
• Consideration of the other side
• Consideration of audience to whom argument is
  given
• Use appropriate tone and diction
• Avoidance of logical fallacies

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Argument The Toulmin Model

• Claim Main point or central message
• thesis statement
• Support Data, evidence, reasons, details
• Warrant Underlying assumptions implied
• but not stated. Reader infers
• assumptions.
• Warrants are based on
• Authority respect for credibility and
  trustworthiness of source
• Substance reliability of facts and evidence
• Motivation values and beliefs of audience and
  writer

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EVALUATING EVIDENCEIN AN ARGUMENT

• Is the evidence
• SUFFICIENT
• REPRESENTATIVE
• RELEVANT
• ACCURATE
• FAIR AND BALANCED

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Impediments to Logic, Good Reasoning, and
Critical Thinking

• LOYALTY loyalty to our own community or group
  see its beliefs as more
• favorable than others
• PROVINCIALISM narrowing our view to identify
  with ideas and interests of
• only our own group
• THE HERD INSTINCT keeping our beliefs and
  actions within societys
• (or our communitys) boundaries
• BACKGROUND BELIEFS
• PREJUDICE AND STEREOTYPING
• SCAPEGOATING problems blamed on a person/group
• PARTISAN MINDSET us vs. them
• SUPERSTITIOUS BELIEFS
• WISHFUL THINKING AND SELF-DECEPTION
• RATIONALIZATION ignore evidence to justify
  actions
• SUPPRESSION avoiding the anxiety of stressful
  thoughts
• DENIAL change our view of the facts of the
  situation to be more positive
• in spite of evidence
• LACK OF A SENSE OF BALANCE OR PRUDENCE

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Inductive and Deductive Reasoning

• Inductive Reasoning
• Reasons from specific to general
• Notices many facts and comes to a general
  conclusion
• No certainty possible
• Deductive Reasoning
• Reasons from general to specific
• Starts with a hypothesis and inserts a fact and
  comes to a conclusion based on hypothesis
• Certainty can be possible if valid and true
  syllogism (say some people)

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INDUCTIVE REASONING

• Reasoning from sensory observation of specific
  facts/evidence to general conclusion
• With inductive reasoning, there can NEVER be
  certainty, because only ONE example can modify or
  refute the conclusion. (This example can come
  from any future event, or events in remote places
  and times we are not able to observe.)
• Based on an accumulation of many facts (one fact
  x)
• Observation of
• x x x x x x x x x x x x x x x x x x x x x x x x
• Equals
• General Statement about Xs in future

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Examples of inductive reasoning

• If I jump off the building, I will fall to the
  ground. (More specifically Every time
  something with weight and mass is released from
  any height, it falls to the ground. Therefore,
  all things fall to the ground (law of gravity).
• Based on an evaluation and observation of
  multiple studies of adolescents who value peers
  more than parents, Judith Rich Harris concludes
  that peers matter more than parents in this age
  group.
• Whenever it snows or rains, it will eventually
  stop snowing or raining.
• George Bush, Sr. made promises during his 1988
  campaign he didnt keep. Bill Clinton made
  promises during his 1992 and 1996 campaigns that
  he didnt keep. George Bush (Jr.) made promises
  in his 2000 and 2004 campaigns that he didnt
  keep. Therefore, the next president in 2008 will
  make promises in his campaign that he very likely
  will not keep.
• So far all U.S. presidents have been male.
  Therefore, the next U.S. president will be male.

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Faulty Inductive Reasoning

• Today I saw an 80 year old lady driving 40 miles
  an hour on 285, a 95 year old man going 50 mph on
  400, and a 70 year old guy going 20 mph on Haynes
  Bridge Road. Conclusion Old people drive slow.
  (This is a stereotype, or logical fallacy of
  inductive origin.)
• Jesse Helms said in the Mexican Foreign Affairs
  Subcommittee (to prevent immigration from
  Mexico) All Latins are volatile. (This is a
  stereotype, or logical fallacy of inductive
  origin.)

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Deductive Reasoning

• Reasoning from general tenets and premises to
  specific conclusions.
• With deductive reasoning, there CAN be certainty.
• Syllogisms follow this format
• Major Premise (general truth about life/humans)
• Minor Premise (specific fact that falls under the
  truth)
• Conclusion (a conclusion that can be drawn about
  the specific fact based on the first
  generalization)

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Syllogism Examples

• Correct Syllogism
• Major Premise All mammals are warm-blooded
  animals.
• Minor Premise No lizards are warm-blooded
  animals.
• Conclusion Therefore, no lizards are mammals.
• Correct Syllogism
• Major Premise All humans are mortal.
• Minor Premise All Greeks are human.
• Conclusion Therefore, all Greeks are mortal.
• Descartes Syllogism (correct)
• Major Premise Existence has be true if one is
  thinking.
• Minor Premise I am thinking.
• Conclusion I think, therefore, I am.

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Syllogisms can be

• Valid or Invalid (reasoning in incorrect order)
• AND
• True or False (reasoning from a faulty major
  premise)

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Examples of Faulty Syllogisms

• FALSE Syllogism (not TRUE -- false major
  premise)
• Major Premise Blondes have more fun
• Minor Premise Mary is blonde, Jane is brunette
• Conclusion Mary has more fun than Jane.
• INVALID Syllogism (not VALID order of reasoning
  is incorrect)
• Major Premise All dogs eat meat
• Minor Premise Bob (a human) eats meat
• Conclusion Bob is a dog.

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Corrections

• Syllogism One
• The first faulty syllogism proceeds from a
  FALSE major premise and therefore can be thrown
  out entirely.
• Syllogism Two
• Major Premise All dogs eat meat
• Minor Premise Rover is a dog.
• Conclusion Therefore, Rover eats meat.

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Valid or invalid? True or False?

• Example One
• Major Premise When it snows the streets get
  wet.
• Minor Premise The streets are getting wet.
• Conclusion Therefore, it is snowing.
• Example Two
• Major Premise If you buy a Ferrari, you will
  instantly be popular.
• Minor Premise Ed just bought a Ferrari.
• Conclusion Ed will achieve instant popularity.
• Example Three
• Major Premise When the batter is dead, the car
  will not start.
• Minor Premise The car will not start.
• Conclusion Therefore, the battery is dead.

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Corrections Valid and True

• Example One
• Major Premise When it snows the streets get
  wet.
• Minor Premise It is snowing.
• Conclusion Therefore the streets are getting
  one.
• Example Two
• Example Two proceeds from the beginning from a
  FALSE major premise (Ferraris give instant
  popularity) and therefore can be thrown out
  entirely.
• Example Three
• Major Premise When the batter is dead, the car
  will not start.
• Minor Premise The battery is dead.
• Conclusion Therefore, the car will not start.

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Some types of syllogisms

• Modus Ponens
• Modus Tollens
• Hypothetical Syllogism
• Disjunctive Syllogism

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Modus Ponens

• If A then B
• A
• Therefore, B
• Examples
• If its spring, then the birds are chirping
• Its spring.
• The birds are chirping.
• If a world government doesnt evolve soon, then
  wars will continue to occur
• A world government isnt going to evolve soon.
• Wars will continue to occur

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Modus Tollens

• If A then B
• Not B
• Not A
• Example
• If its spring then the birds are chirping
• The birds arent chirping
• Therefore, it isnt spring.

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Hypothetical Syllogism

• If A then B
• If B then C
• If A then C
• Example
• If we successfully develop nuclear fusion power,
  then power will become plentiful and cheap.
• If power becomes cheap and plentiful, then the
  economy will flourish.
• If we successfully develop nuclear fusion power,
  then the economy will flourish.

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Disjunctive Syllogism

• A or B
• Not A
• B
• Example
• Either McCain won in 2008 or Obama did.
• McCain didnt win.
• Obama did win.

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LOGICAL FALLACIES

• Circular Reasoning/Begging the Question
  Promising support for your claim but providing
  none
• Bandwagon/ Inviting readers to accept a claim
  because everyone else does or because the
  prestigious group does
• Argument from authority Inviting readers to
  accept a claim because because the claim is put
  forth by someone in a position of authority
  though the authority is invalid.
• Slippery Slope forecasting a series of events
  (usually disastrous) that will befall one if the
  first stated step is taken.
• Straw Man Inserting a false or unrelated
  premise into an argument, and then proving the
  false or unrelated premise wrong as a claim that
  the initial argument is wrong.
• Appeal to Fear scaring the reader to your point
  of view
• Appeal to Pity substituting emotions for
  reasoning.
• Appeal to Force abandoning reason and using or
  threatening strong arm methods by means of the
  political or physical power of the enforcer
  might makes right

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• Red Herring introducing an irrelevant issue
  intended to distract readers from the relevant
  issues going off on a tangent.
• Self Contradiction using two premises that
  cant be simultaneously true
• False Cause or Post Hoc Fallacy (from Latin
  post hoc, ergo propter hoc, meaning after this,
  therefore because of this) assuming that
  because A preceded B, then A must have caused B.
• False Analogy Assuming that because two things
  are alike in similar ways, they must be alike in
  other ways
• Either/Or Fallacy (False Dilemma) assuming that
  a complicated question has only two answersone
  good, and one bad, both good, or both bad.
• Hasty Generalization making a claim on the
  basis of inadequate evidence. Generalizing about
  something on the basis of too little evidence.
• Stereotyping is a type of Hasty Generalization
  applied to a group of people.
• Sweeping Generalization making an insupportable
  statement, often using absolute statements such
  as all, always, never, and no one.
• Ad Hominem (attacking the man) attacking the
  qualities of the people holding an opposing view
  rather than the substance of the view itself.

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• Guilt by Association kind of ad hominem
  attack implying that an individuals arguments,
  ideas, or opinions lack merit because of that
  persons activities, interests or associates.
• Non Sequitur (Latin It does not follow)
  linking two or more ideas that in fact have no
  logical connection the statement does not follow
  logically from what has just been said
• Card Stacking/Special Pleading Ignores evidence
  on the other side of the question only selecting
  those items that will build the best (or worst)
  possible case.
• Oversimplification/Reductive Fallacy
  Oversimplifying (reducing) the relation between
  causes and effects
• Quibbling Nitpicking at insignificant or
  possible errors in someone elses basically valid
  and sensible argument
• Language Fallacies
• Emotional, biased, or slanted language
• Equivocation
• Ambiguity or obfuscation
• Euphemism or PC, Doublespeak
• Pretentious language, bureaucratic language
• Jargon

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What is logically wrong with the following
statements?

• The Bible is true because it says so.
• Boxing is dangerous because it is an unsafe sport.

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Circular Reasoning/Begging the Question

• A.
• Therefore, A.
• promising support/evidence/reasoning for your
  claim but providing none
• Promising
• Claim Support
• Delivering
• Claim
• (Support)

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??

• Billy Joe is honest therefore, he will get a
  good job

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Non Sequitur

• (Latin for It does not follow) linking two or
  more ideas that in fact have no logical
  connection
• Missing is the unstated assumption that honest
  people get good jobs which is not always true.

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• Bill Clinton smoked pot when he was in college
  therefore, he should not be president of the
  United States.
• Bill Clinton is a womanizer therefore, he should
  not be president of the United States.

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Ad HominemAttacking the Man

• Attacking the personal qualities of the people
  holding an opposing view rather than the
  substance of the view itself
• In this case, Clinton may well be an excellent
  president and policy maker even though we may
  prefer not to have him as our husband.

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• John Kerry protested at the same anti-war rally
  as Hanoi Jane therefore, he should not be
  elected president.

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Guilt by Association

• A kind of ad hominem attack implying that an
  individuals arguments, ideas, or opinions lack
  merit because of that persons activities,
  interests or associates

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• Professor Perkins, if I dont make an A in your
  class I wont get my HOPE scholarship next
  semester.
• A plaintiffs attorney brings his injured client,
  who is seeking compensatory damages, into the
  courtroom and plays up the injury in front of the
  jury (A Civil Action)
• Socrates at his death trial
• My friend, I am a man and like other men, a
  creature of flesh and blood, and not of wood and
  stone as Homer says and I have a family, yes,
  and sons, O Athenians, three in number, one
  almost a man, and two others who are still young
  and yet I will not bring any of them here to
  petition you for acquittal.

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Appeal to Pity

• Substituting emotions for reasoning an appeal to
  emotion, in which the altruism and mercy of the
  audience are appealed to

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??

• George Bush is the candidate that can stop
  another terrorist attack on the United States if
  you vote for John Kerry, be prepared for another
  9/11.
• When Lyndon Johnson was running for president,
  his team ran a commercial of a little girl in a
  field holding a daisy, then an atomic bomb went
  off in the background.

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Appeal to Fear

• Tries to scare the reader to your point of view

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• When Reagans attorney general was under media
  attack, Howard Baker, then White House Chief of
  Staff, said to his staff
• The President continues to have confidence in
  the Attorney General and I have confidence in the
  Attorney General and you ought to have confidence
  in the Attorney General, because we work for the
  President and because thats the way things are.
  If anyone has a different view of that, or any
  different motive, ambition or intention, he can
  tell me about it because were going to have to
  discuss your status. (White House Orders
  Silence on Meese, Washington Post, 29 April
  1988, qtd. in Copi and Cohen)

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Appeal to Force

• Abandoning reason to convince someone of your
  point of view and instead using or threatening
  strong arm methods by means of the political or
  physical power of the enforcer might makes
  right

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??

• Mom, I should be able to go to Underground
  Atlanta to see the free Weezer concert that lasts
  til 1 AM all my friends moms are letting them
  go.
• Despite the cost, impending gas crisis, and the
  harm to the environment, it is desirable to own
  an SUV because successful people do.
• More people in America drink Budweiser than any
  other beer.

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Bandwagon

• Inviting readers to accept a claim because
  everyone else does or because a prestigious group
  does

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??

• Television commercials that advertise their
  product using famous stars, for example, Ray
  Charles advertising Coke.
• Matt Damon should write a novel about the CIA
  since he was in The Bourne movie trilogy.

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False Authority

• Citing the opinion of an expert who has no real
  claim to expertise on the topic

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??

• You should go on the Lose Weight Overnight diet
  plan because Mary Braddock and Tom Jones lost 100
  pounds total in three months on it.

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Card StackingSpecial Pleading

• Ignores evidence on the other side of the
  question
• Only selecting those items that will build the
  best (or worst) possible case.

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??

• The new mayor took office last January and crime
  in the streets has already increased 25 percent.
• A new weather satellite was launched last week
  and it has been raining ever since.
• After that black cat crossed my path this
  morning, I got into a car accident. That cat was
  bad luck.

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Post Hoc FallacyFalse Cause

• (from Latin post hoc, ergo propter hoc, meaning
  after this, therefore because of this)
  assuming that because A preceded B, then A must
  have caused B.

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??

• Since those book are about the same length and
  cover the same material, one is probably as good
  as another.
• Both of the candidates are extremely wealthy,
  born within the same decade, went to the same
  college, and were members of the same secret
  society, so both should probably do about the
  same in office.

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False Analogy

• Using a comparison in which two things are alike
  in one way to justify that they will be alike in
  another way. However, the similarities are
  irrelevant to the claim the analogy is intended
  to support.

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• America love it or leave it.
• We have only two choices ban nuclear weapons or
  destroy the earth.
• Either we go to war against Iraq, or the United
  States will suffer another terrorist attack.

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Either/Or Fallacy and False Dilemma

• Stating that only two alternatives exist when in
  fact there are more than two

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??

• Teenagers are reckless drivers
• America is the best place to live (stated
• by one who has rarely visited other
• countries)
• All Latins are volatile people
• -- Rep. Jesse Helms to the Mexican Foreign
  Affairs Subcommittee (to prevent immigration from
  Mexico)

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Hasty Generalization

• Generalizing or making a claim on the basis of
  inadequate evidence.

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??

• Why spend money on solving the problem of pandas
  becoming extinct when we should be concerned
  about the plight of the homeless?
• How can we worry about a few terrorists when we
  ought to be doing something about acid rain?

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Red Herring

• Introducing an irrelevant issue intended to
  distract readers from the relevant issues going
  off on a tangent

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• He got into Yale because hes rich and his daddy
  went there.
• The events of September 9/11 are purely the
  result of Al Qaedas and Osama bin Ladens
  craziness.

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OversimplificationReductive Fallacy

• Oversimplifying (reducing) the relation between
  causes and effects.

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??

• If we make handguns illegal, the state will gain
  too much power and eventually put us all in
  concentration camps for the slightest infraction.
  
• If we legalize marijuana, eventually everyone
  will start smoking it regularly (an after-dinner
  smoke) and then theyll want to go on to more
  kinds of drugs soon heroin will become legal
  and most of America will become heroine addicts.

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Slippery Slope

• forecasting a series of events (usually
  disastrous) that will befall one if the first
  stated step is taken

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??

• Only when nuclear weapons have finally destroyed
  us will we be convinced of the need to control
  them.

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Self Contradiction

• Using two premises that cant be simultaneously
  true

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• The Bush campaign leaked faked documents to CBS
  news about Bushs AWOL during his national guard
  service. CBS accepted the documents without
  checking on them but the documents were later
  shown to be faked. The White House attacked CBS
  (and its liberal agenda) for presenting the
  documents to the public though it never denied
  Bushs AWOL from service. The issue, however,
  was dropped.

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Straw Man

• Inserting a false or unrelated premise into an
  argument, and then proving the false or unrelated
  premise wrong as a claim that the initial
  argument is wrong.

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??

• I am firm, you are stubborn, he is pigheaded.
  Bertrand Russell
• Friendly fire military term for killing your
  own team by mistake
• Collateral damage military term for people
  who are inadvertently killed or property
  inadvertently destroyed in warfare

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Language Fallacies

• Emotional or biased language
• Equivocation
• Ambiguity or obfuscation
• Euphemism or PC language
• Doublespeak
• Pretentious language
• Bureaucratic language
• Jargon

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• The object of reasoning is to find out, from the
  consideration of what we already know, something
  else which we do not know. -- Charles Sanders
  Peirce
• A simple person believes every word he hears a
  clever one understands the need for truth.
  Proverbs 1415
• Those who do not remember the past are condemned
  to relive it. --- George Santayana
• (One government official to another)
  Congratulations Dave! I dont think Ive read a
  more beautifully evasive and subtlely misleading
  statement in all my years in government.
  cartoon in the New Yorker by Stevenson
• Read not to contradict and confute, nor to
  believe and take for granted but to weigh and
  consider. Francis Bacon
• Ignorance of reality provides no protection
  from it. Harold Gordon
• Every man is encompassed by a cloud of
  comforting convictions, which move with him like
  flies on a summer day. Bertrand Russell
• Arguments, like men, are often pretenders.
  Plato
• There are lies, damn lies, and statistics.
  Benjamin Disraeli
• Every dogma has its day. Abraham Rotstein
• Nothing is so firmly believed as what we least
  know. Montaigne
• Populus vult decipi. (The people want to be
  deceived.) Ancient Roman saying
• Logic is only the beginning of wisdom. --
  Spock, Star Trek V, The Undiscovered Country
• "If I release a hammer on a positive gravity
  planet, I do not have to watch it to know that it
  willfall." Spock, Star Trek TV seriies,
  episode The Court Martial
• When an idea is wanting a word can always be
  found to take its place. Goethe
• He who defines the terms wins the argument.
  Chinese proverb
• There is no expedient to which a man will not
  resort to avoid the real labor of thinking.
  Sir Joshua Reynolds
• There are no dull subjects. There only dull
  writers. -- H. L. Mencken
• Advertising is legalized lying. H.G. Wells

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Works Cited and Works Consulted

• Copi, Irving M. and Carl Cohen. Introduction to
  Logic, 10th ed.
• Upper Saddle River, NJ Prentice Hall, 1998.
• DeVry/Alpharetta Coll 147/149 Resource Notebook.
  General Education
• Department. Alpharetta, GA DeVry
  University, 2004.
• Hodges, John C. Mary Whitten. Harbrace College
  
• Handbook, 10th ed. New York HBJ, 1986.
• Kahane, Howard and Nancy Cavender. Logic and
• Contemporary Rhetoric The Use of Reason in
• Everyday Life. Belmont, CA Wadsworth/Thomson
• Learning, 2002.
• Troyka, Lynn Quitman. Simon Schuster Handbook
  for
• Writers, 5th ed. Upper Saddle River, NJ
  Prentice
• Hall, 1999.

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