Logical Fallacies

logical fallacieslogical fallacieslogical fallacieslogical fallacies

THE ART OF DEBATETHE ART OF DEBATE

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What is a logical What is a logical fallacy?fallacy?

What is a logical What is a logical fallacy?fallacy?

Fallacies are common errors in reasoning that Fallacies are common errors in reasoning that

will undermine the logic of your argument. will undermine the logic of your argument.

Fallacies can be either illegitimate arguments Fallacies can be either illegitimate arguments

or irrelevant pointsor irrelevant points

They are often identified because they lack They are often identified because they lack

evidence that supports their claim. evidence that supports their claim.

Avoid these fallaciesAvoid these fallacies

Types of Logical Types of Logical FallaciesFallacies

Types of Logical Types of Logical FallaciesFallacies

SLIPPERY SLOPE SLIPPERY SLOPE

HASTY GENERALIZATIONHASTY GENERALIZATION

POST HOC ERGO PROPTER HOCPOST HOC ERGO PROPTER HOC

GENERIC FALLACYGENERIC FALLACY

BEGGING THE CLAIMBEGGING THE CLAIM

CIRCULAR ARGUMENTCIRCULAR ARGUMENT

EITHER/ OREITHER/ OR

AD HOMINEMAD HOMINEM

AD POPULUMAD POPULUM

RED HERRINGRED HERRING

STRAW MANSTRAW MAN

MORAL EQUIVALENCEMORAL EQUIVALENCE

Slippery SlopeSlippery SlopeSlippery SlopeSlippery Slope

This is a conclusion based on the premise This is a conclusion based on the premise

that is that is AA happens, then eventually happens, then eventually

through a series of small steps, through through a series of small steps, through BB, ,

CC, ...., ....XX, , YY, , ZZ will happen, too, basically will happen, too, basically

equating equating AA and and ZZ. So , if we don’t want . So , if we don’t want ZZ

to occur, to occur, AA must not be allowed to occur must not be allowed to occur

either. either.

Slippery SlopeSlippery SlopeSlippery SlopeSlippery SlopeThis is a conclusion based on the premise that is This is a conclusion based on the premise that is AA happens, then eventually happens, then eventually

through a series of small steps, through through a series of small steps, through BB, , CC, ...., ....XX, , YY, , ZZ will happen, too, will happen, too,

basically equating basically equating AA and and ZZ. So , if we don’t want . So , if we don’t want ZZ to occur, to occur, AA must not be must not be

allowed to occur either. allowed to occur either.

Example:Example: If we ban Hummers because they are bad If we ban Hummers because they are bad

for the environment, eventually the government will for the environment, eventually the government will

ban all cars, so we should not ban Hummers.ban all cars, so we should not ban Hummers.

In this example the author is equating banning In this example the author is equating banning

Hummers with banning all cars, which is not the Hummers with banning all cars, which is not the

same thing.same thing.

Hasty Hasty GeneralizationGeneralization


This is conclusion based on insufficient or This is conclusion based on insufficient or

biased evidence. biased evidence.

In other words, you are rushing to a In other words, you are rushing to a

conclusion before you have all the conclusion before you have all the

relevant facts.relevant facts.



This is conclusion based on insufficient or This is conclusion based on insufficient or

biased evidence. biased evidence.

In other words, you are rushing to a conclusion In other words, you are rushing to a conclusion

before you have all the relevant facts.before you have all the relevant facts.

Example: Example: Even though it’s only the first day, I Even though it’s only the first day, I

can tell this is going to be a boring course.can tell this is going to be a boring course.

Write your own fallacy.Write your own fallacy.

post hoc ergo post hoc ergo propter hocpropter hoc


This is the conclusion that assumes that if This is the conclusion that assumes that if

AA occurred after occurred after BB then then BB must have must have

caused caused AA



This is the conclusion that assumes that if This is the conclusion that assumes that if AA

occurred after occurred after BB then then BB must have caused must have caused AA

ExampleExample: I drank bottled water and now I am : I drank bottled water and now I am

sick, so the water must have made me sick.sick, so the water must have made me sick.

In this example the author assumes that if one In this example the author assumes that if one

event chronologically follows another the first event chronologically follows another the first

event must have caused the second. event must have caused the second.


generic fallacygeneric fallacygeneric fallacygeneric fallacy

A conclusion is based on an argument that A conclusion is based on an argument that

the origins of a person, idea, institution, or the origins of a person, idea, institution, or

theory determine its character, nature or theory determine its character, nature or

worth.worth.

generic fallacygeneric fallacygeneric fallacygeneric fallacy

A conclusion is based on an argument that A conclusion is based on an argument that

the origins of a person, idea, institution, or the origins of a person, idea, institution, or

theory determine its character, nature or theory determine its character, nature or

worth.worth.

Example: Example: The Volkswagen Beetle is an evil The Volkswagen Beetle is an evil

car because it was originally designed by car because it was originally designed by

Hitler’s army.Hitler’s army.


Begging the claimBegging the claimBegging the claimBegging the claim

The conclusion that the writer should The conclusion that the writer should

prove is validated within the claimprove is validated within the claim

Begging the claimBegging the claimBegging the claimBegging the claim

The conclusion that the writer’s proof is The conclusion that the writer’s proof is

validated within the claimvalidated within the claim

Example:Example: Filthy and polluting coal should Filthy and polluting coal should

be banned.be banned.


Circular argumentCircular argumentCircular argumentCircular argument

This restates the argument rather than This restates the argument rather than

actually proving it.actually proving it.

Circular argumentCircular argumentCircular argumentCircular argument

This restates the argument rather than This restates the argument rather than

actually proving it.actually proving it.

Example: Example: George Bush is a good George Bush is a good

communicator because he speaks communicator because he speaks

effectively.effectively.


Either/orEither/orEither/orEither/or

This is a conclusion that oversimplifies the This is a conclusion that oversimplifies the

argument by reducing it to only two sides argument by reducing it to only two sides

or choices.or choices.

Either/orEither/orEither/orEither/or

This is a conclusion that oversimplifies the This is a conclusion that oversimplifies the

argument by reducing it to only two sides argument by reducing it to only two sides

or choices.or choices.

Example:Example: We can either stop using cars We can either stop using cars

or destroy the earth.or destroy the earth.


Ad HominemAd HominemAd HominemAd Hominem

This is an attack on the character of a This is an attack on the character of a

person rather than their opinions or person rather than their opinions or

argumentsarguments

Ad HominemAd HominemAd HominemAd Hominem

This is an attack on the character of a This is an attack on the character of a

person rather than their opinions or person rather than their opinions or

argumentsarguments

Example: Example: Green Peace’s strategies aren’t Green Peace’s strategies aren’t

effective because they are all dirty, lazy effective because they are all dirty, lazy

hippies.hippies.


Ad PopulumAd PopulumAd PopulumAd Populum

This is an emotional appeal that speaks to This is an emotional appeal that speaks to

positive (such as patriotism, religion, positive (such as patriotism, religion,

democracy) or negative (such as terrorism democracy) or negative (such as terrorism

or fascism) concepts rather than the real or fascism) concepts rather than the real

issue at handissue at hand

Ad PopulumAd PopulumAd PopulumAd Populum

This is an emotional appeal that speaks to This is an emotional appeal that speaks to

positive (such as patriotism, religion, positive (such as patriotism, religion,

democracy) or negative (such as terrorism or democracy) or negative (such as terrorism or

fascism) concepts rather than the real issue at fascism) concepts rather than the real issue at

handhand

Example:Example: If you were a true American you If you were a true American you

would support the rights of people to choose would support the rights of people to choose

whatever vehicle they want.whatever vehicle they want.


Red HerringRed HerringRed HerringRed Herring

This is a diversionary tactic that avoids This is a diversionary tactic that avoids

the key issues, often by avoiding opposing the key issues, often by avoiding opposing

arguments rather than addressing them.arguments rather than addressing them.

Red HerringRed HerringRed HerringRed Herring

This is a diversionary tactic that avoids This is a diversionary tactic that avoids

the key issues, often by avoiding opposing the key issues, often by avoiding opposing

arguments rather than addressing them.arguments rather than addressing them.

Example:Example: The level of mercury in seafood The level of mercury in seafood

may be unsafe, but what will fishers do to may be unsafe, but what will fishers do to

support their families?support their families?


Straw manStraw manStraw manStraw man

This move oversimplifies an opponent’s This move oversimplifies an opponent’s

viewpoint and then attacks that hollow viewpoint and then attacks that hollow

argument.argument.

Straw manStraw manStraw manStraw man

This move oversimplifies an opponent’s This move oversimplifies an opponent’s

viewpoint and then attacks that hollow viewpoint and then attacks that hollow

argument.argument.

People who don’t support the proposed state People who don’t support the proposed state

minimum wage increase hate the poor.minimum wage increase hate the poor.


Moral EquivalenceMoral EquivalenceMoral EquivalenceMoral Equivalence

This fallacy compares minor misdeeds This fallacy compares minor misdeeds

with major atrocities.with major atrocities.




Example:Example: That parking attendant who That parking attendant who

gave me a ticket is as bad as Hitler.gave me a ticket is as bad as Hitler.

Logical Fallacies

Spiritual

Transcript of Logical Fallacies