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This paper describes "bad" arguments. Arguments that many people use -- particularly on internet / Compuserve LISTSERVs and forums, which are simply not persuasive to anyone but "the faithful."

This paper is "work in process" and is incomplete. Comments welcomed.

Three references to books which describe these arguments:

1. THE POWER OF LOGICAL THINKING, by Marilyn vos Savant. St. Martin's Press, New York. 1996. See particularly pages 75 & following.

2. THE DEMON-HAUNTED WORLD, Carl Sagan (ref to be cited later)

3. UNDERSTANDING ARGUMENTS, by Robert J. Fogelin and Walter Sinnott-Armstrong, Fourth Edition, 1991; Harcourt-Brace-Jovanovich, Inc. First published in 1978. College text book.

Marilyn vos Savant cites the following types of argumentative fallacies:

1. Verbal -- one or more words used are ambiguous

        a. Equivocation; same word; two or more definitions:

A person can have a germ of an idea.
Germs cause diseases.
Therefore ideas can cause diseases.

        b. Amphiboly; problem with the sentence construction:

I'm having Bob Jones for dinner tonight.

        c. Accent; the wrong word is emphasized:

A snake can only eat green frogs.

        d. Figure of speech; words similar in form are similar in sense:

Wool sweaters shrink when they get wet.
Therefore, sheep shrink in the rain.

        e. Composition; A thing true of the parts is true of the whole:

One new tax can generate lots of added government revenue.
Therefore a lot of new taxes would eliminate the budget deficit.

        f. Division; A thing true of the whole is true of its parts:

A musical group performs well and is wildly popular.
Therefore the drummer can leave the group and do well on his own.

2. Formal fallacies.

        a. Affirming the consequent; Assuming the antecedent:

An AIDS patient has a low T cell count.
Susan has a low T cell count.
Therefore, Susan has AIDS.

        b. Denying the antecedent; A twin of the above:

If a person has AIDS, his T cell count will be low.
Peter has been found to not have AIDS.
Therefore Peter's T cell count is not low.

        c. Four terms; a syllogism that uses equivocation in the middle:

Plants differ from animals in that they bloom in the spring.
Some people bloom in the spring too.
Therefore, people are plants.

        d. Undistributed middle; The middle term does not link correctly:

Truffles are found by dogs trained to locate them by scent.
Criminals are also found by dogs trained to locate them by scent.
Therefore, criminals are truffles.

        e. Illicit minor; The subject of the conclusion is too broad:

Giant sequoias are the largest organisms alive.
All giant sequoias are trees.
Therefore all trees are the largest organisms alive.

        f. Illicit major; The predicate of the conclusion is too broad:

Banana trees are actually herbaceous plants.
All bananas are fruits.
Therefore no fruits grow on trees.

3. Material fallacies.

        a. Ignoratio elenchi; An irrelevant conclusion:

        aa. Argumentum ad hominem; Opponent is attacked:

Dr. Gish's theory is wrong because Dr. Gish is a liar.

        ab. Tu quoque; Opponent is attacked by a countercharge:

Darwin's theory is wrong because he didn't publish it until another
scientist had a similar idea and was likely to get all the credit.

        ac. Argumentum ad Populum. An appeal to popular passion:

Evolution is hogwash, preached by godless scientists who want to
turn this country into a "free love" state.

        ad. Argumentum ad verecundiam; An appeal to authority:

Evolution is a fact, because Dr. Stephen Gould says so.

        ae. Argumentum ad misericordium; An appeal to pity:

Abortion is wrong; how can one stand to kill an innocent baby?

        af. Argumentum ad baculum; An appeal to force:

Christianity is correct; if you don't agree we will burn you at the stake.

        ag. Argumentum ad ignorantium; An appeal to ignorance:

There is no proof that humans descended from rabbits, but there is 
also nothing in the fossil record to disprove this hypothesis either. 
Who knows what will turn up next?

4. The fallacy of petitio principii (begging the question)

Miracles can't happen because they would defy the laws of nature.

5. The fallacy of circus in probando; The circular argument:

The fact of evolution must be true because so many scientists
could not all be wrong.

6. The fallacy of secundum quid; Two kinds:

        a. Direct accident; inappropriate application of a general principle:

It appears that fish developed lungs and moved onto the land. Therefore 
my guppies at home will someday be found walking around the kitchen.

        b. Converse accident; the reverse of the above:

Because my guppies will never leave the water, it follows that
no fish ever did so.

7. The fallacy of post hoc, ergo propter hoc. Hasty generalization:

William Jennings Bryan was fatally stricken by illness and died shortly after
the Scopes trial. Therefore, it follows that God was punishing him for
defending nonsense.

8. The fallacy of reductio ad absurdum; 

Scientists have open minds. Anyone who categorically denies the authority
of the church has a closed mind. But Darwin's theory categorically 
denied the authority of the church. Hence Darwin had a closed mind. Hence,
Darwin was not a scientist.

9. The fallacy of plurimum interrogationum; The peculiar question:

Mr. Clinton, have you stopped beating your wife?

10. The fallacy of non-sequitur; Conclusion does not follow from the argument:

Because humans look so much like apes, evolution is a fact.

Marilyn's book is recommended; some of the examples above are hers; others are
mine. She has much more to say (and explain) on each of the above!

Here are a couple bad arguments I've seen recently. Can you identify
what kind (from the list above) each one is?

"All Eskimos walk in single file. I saw one once and that is what he was doing.

"The ACLU's stated goal is to eliminate God from the schools. I read an
article once in the LA Times in which the reporter quoted an ACLU speaker
as stating this."

"More people have been murdered through abortions than died in the
Holocaust. Therefore, we need a law to prohibit abortions."

"A partial-birth abortion procedure is hideous to watch. Therefore we need
a law to prohibit partial birth abortions."

Yours for logical thinking. 


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