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    FALLACIESEngel, S. Morris. 2000. With Good Reason: An

    introduction to Informal Fallacies. 6th ed. Bedford.

  • *Fallacy of Presumption:

    "Justice requires higher wages because it is right that people should earn more."

    This amounts to: "justice requires higher wages because justice requires higher wages.

    God exists! How do you know? The Bible says so. How do you know that what the Bible says is true? Because the Bible is the word of God!

    --Begging the question: (petitio principii)

    The argument uses the conclusion that it seeks to establish. It

    assumes the conclusion in its premises.

  • *Fallacies of presumption:

    "Since I'm not lying, it follows that I'm telling the


    Bill: I enjoy only good books.

    Tom: How do you know when theyre good?

    Bill: If theyre not good, I dont enjoy them.

    -- Circular definition:

    The definition includes the term being defined

    as a part of the definition; Using the concluding claim

    as evidence to support the conclusion.

  • *Fallacies of relevance:

    "If we lower the drinking age from 21 to 18,

    then what next? 16 year olds being allowed to

    drink? 14 year olds?"

    "If we allow the French to influence us, we'll

    soon be eating nothing but snails and garlic."

    --Slippery slope:

    Supposing that a single step

    in a particular direction

    must lead to the extreme position.

  • Fallacies of presumption:

    "After Ketchup was considered a serving of vegetables in school meals, math scores dropped nation-wide. Therefore, ketchup causes math scores to drop."

    -- Post hoc ergo propter hoc: (Post hoc for short.

    Latin: "after this, therefore because of this.")

    Because one thing follows another,

    it is held to cause the other.FORM:

    Event C happened immediately prior to event E.

    Therefore, C caused E.


  • *Fallacies of presumption:

    "In K-12 children, neater handwriting causes

    larger feet.

    The number of cases of drowning increases

    as the sale of ice cream increases. So eating

    ice cream must cause drowning.

    -- Cum hoc ergo propter hoc:

    Assumes events which occur together are causally connected,

    and there is no room for coincidence or for other causal

    factors. FORM: Events C and E both happened at the same time.

    Therefore, C caused E.

  • *Fallacies of relevance:

    "If you are not with us, you are against

    us." -W


    Presenting only two alternatives

    where others exist;

    black and white thinking.


  • *Fallacies of relevance:

    "How can you condone usury? You're a

    Christian, and Christ drove the money-lenders

    from the temple."

    As an opera-lover, you will be the first to agree

    that we need more subsidy for the arts."

    -- Argumentum ad Hominem:

    Attacking the arguer

    rather than the argument itself.

    It also includes invoking the proponents position.


  • *Fallacies of relevance:

    "Since you based your theory of Bigfoot

    on stories from The National Enquirer,

    the theory must be false.

    The war on drugs started from strict

    Puritanical heritage. So we dont have

    to encourage drug control.

    -- The genetic fallacy: (p. 89)

    Attacking the source of the argument

    rather than the argument itself. It is a fallacy,

    because how an idea originated is irrelevant to its validity.

  • *Fallacies of relevance:

    "You can't tell me smoking is bad when

    you've been smoking for thirty years."

    -- Tu Quoque: ("you also")

    Undermining a case by claiming

    that its proponent is himself guilty of what he talks of.

  • Anecdotal evidence

    Anecdotes and stories

    These are events that happen to someone, or

    that are told to them, with no attempt at any

    scientific analysis. Some are simply stories,

    events that did not really happen or that have

    been significantly altered (for example urban

    legends). They are useful for adding interest, and

    in illustrating points, but they should not be used

    to make generalizations.

    "This is third day in a row that we've had a record

    high temperature. Global warming must be real." 12

  • *Fallacies of relevance:

    "The credit card company will take my

    late fee off. Otherwise I'll be so broke I

    can't pay them anything."

    --Wishful thinking:

    Rejecting a claim solely because

    we do not wish it to be true.

  • *Fallacies of relevance:

    We should liberalize the laws on


    No. Any Society with unrestricted

    access to drugs loses its work ethic and

    goes only for immediate gratification.

    -- Straw Man:

    A deliberate over-statement of an opponent's position.

    Stating a position that no one holds.

  • *Fallacies of relevance:

    "It cleans your teeth white! Yes, that's

    right-- whiter than white!"

    -- Argumentum ad Nauseum:

    Repetition of a point,

    often by exaggerating or slightly changing the point.

  • *Fallacies of language:

    "Hitler summons war lords!

    "Scotland stole a goal in the first half, but

    England's efforts were rewarded. . ."

    --Loaded words: (also emotive argument)

    The deliberate use of prejudiced terms

    to conjure a more favorable

    or hostile response.


    "This must be a good orchestra

    because each member is a talented


    Composition:Claiming that what is true for individual

    members of a class

    is also true for the class as a whole.


    "Germany is a militant country. Thus, each

    German is militant.

    "Because the brain is capable of

    consciousness, each neural cell in the brain

    must be capable of consciousness."

    Division:Attributing to the individuals in a group

    something that is only true of the group as a unit.


    "All child-murderers are inhuman, thus, no child-murderer is human.

    "My dog's got no nose/ How does he smell?/ Terrible!"

    Equivocation:Using words ambiguously;

    equivocal words have more than one meaning.


    You are not entitled to your opinion.

    Equivocation:Using words ambiguously;

    equivocal words have more than one meaning.


    1. If someone is entitled to an opinion

    then her opinion is well-supported by

    the evidence. (This is precisely what it

    means to be entitled to an opinion).

    2. I am entitled to my opinion (as is

    everyone in a democratic society).

    3. Therefore, my opinion is well

    supported by the evidence.


    Consider the true premise: If there is

    fire, oxygen is present.

    "Oxygen is present, therefore there is fire.

    "If I drop an egg, it breaks. This egg is broken,

    so I must have dropped it."

    --Affirming the consequent: (Remember: biconditional)

    Believing that the consequent (the second phrase)

    necessarily entails the antecedent.


    Consider the premise: If there is fire, oxygen is


    There is no fire, therefore there is no oxygen.

    Consider the premise: If I am hungry in the

    morning, I will eat breakfast.

    I am not hungry in the morning, therefore I will

    not eat breakfast.

    --Denying the antecedent:

    Believing that when the antecedent is false,

    the consequent must be false also.


    The apples on the top of the box look

    good. The entire box of apples must be


    --Unrepresentative sample:

    The sample used relevantly different

    from the population as a whole.

  • "I'm backing Hillary Clinton on this one.

    She can't be wrong all the time.

    Im betting red on the Roulette table.

    The last five times was black, so its

    bound to be red soon.

    --Gambler's Fallacy:

    Believing the next outcome

    will somehow be influenced by the last outcome.

    This only applies to cases of independent trials,

    like rolling the dice.


  • *Fallacies of relevance:

    "We don't know what caused the door

    to slam, therefore it was a ghost.

    We dont have proof that God exists,

    therefore he does not exist.

    -- Argument from ignorance:

    Using the lack of knowledge

    of any alternatives to

    justify the truth of a claim.


    "I met the ambassador riding his horse. He was snorting and steaming, so I gave him a lump of sugar"

    "Helicopter powered by human flies" "The anthropologists went to a remote area and

    took photographs of some native women, but they weren't developed."

    "One morning I shot an elephant in my pajamas. How he got into my pajamas I'll never know." --Groucho Marx

    -- Amphiboly:

    Sentence constructions are ambiguous; the whole meaning of a

    statement can be ta


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