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Fallacies
how not to argue logically
Elements of Logic
Spring 2013
束anti-copyright: do what you want with this
informal fallacies
1. fallacies of relevance
These have in common the use of irrelevant information to try
to persuade us into believing the conclusion.
2. fallacies of presumption
These make additional unstated assumptions not warranted by
the context.
3. fallacies of ambiguity
These rest on the multiple meanings that often are attached to
individual words and concepts.
appeal to ignorance
Nobody has ever proved that God exists,
therefore God does not exist.
appeal to ignorance
There is no evidence of weapons of mass
destruction in Iraq, thus there are really are no
weapons of mass destruction in Iraq.
appeal to (illegitimate) authority
Lance Armstrong says that we should all do our
part to cut carbon emissions, so we should do so.
appeal to (illegitimate) authority
Joe Camel says that smoking is good for you.
Therefore, all of those stories about smoking
being a health risk are wrong.
argument against the person
abusive ad hominem
Rush Limbaugh is a big fat liar! That is why you
should not pay any attention to his arguments.
argument against the person
circumstantial ad hominem
Xandra is wearing a leather coat, calf-skin boots
and a fur hat. So we can dismiss her arguments
that animals should have rights.
argument against the person
tu quoque: Youre one too!
Rush Limbaugh and his current wife have six
divorces between the two of them. So we can
dismiss his arguments about why marriage should
be forever.
appeal to emotion
A world without God would be a cold and
meaningless place, in which human lives have
very little signi鍖cance. Therefore religious belief
must have some basis in reality.
appeal to pity
I should not be held responsible for killing my
wife. After all she was in bed with another man
when I came home.
appeal to force
Either I get a good grade in this class or you are
a dead man, professor.
irrelevant appeal
red herring
I fail to see how helping out starving people in
Africa is important. After all, there are plenty of
hungry people right here at home.
irrelevant appeal
straw person
Those baby killing Democrats are proposing
more health care legislation. We can safely say
that it should be opposed.
irrelevant appeal
non sequitur: It does not follow.
The Patriots lost to the Ravens in the playo鍖s.
Thus football is a really stupid sport.
fallacies of relevance
1. appeal to ignorance
2. appeal to illegitimate authority
3. argument against the person
4. appeal to emotion
5. appeal to pity
6. appeal to force
7. irrelevant appeal
complex question
Have you stopped beating your kids?
complex question
Do you love me?
false cause
post hoc ergo propter hoc after which therefore because of which
Yesterday I had a cold, so I drank a bottle of
whiskey. Now I feel better. Thus whiskey cures
colds.
begging the question
You should be a Christian. If not, as the Bible
suggests, you are going to end up in Hell.
accident
stereotyping
Bridget is a woman. Thus she should not serve
in combat positions in the military.
accident
genetic fallacy
Biologists say we are descended from apes. But
apes are dumb and we are smart, so those
biologists must be wrong.
converse accident (hasty generalization)
That person from Massachussetts is a terrible
driver. So beware of all people with
Massachussetts plates on their car.
suppressed evidence
The shale gas boom is great for the economies
of New York and Pennsylvania. After all there
are lots of new jobs drilling for gas as a result.
false dichotomy (false dilemma)
Either you are in favor of attacking Iran or you
are un-unpatriotic. Since you are not in favor of
an attack, you must be un-patriotic.
fallacies of presumption
1. complex question
2. false cause
3. begging the question
4. accident
5. converse accident (hasty generalization)
6. suppressed evidence
7. false dichotomy
equivocation
Being free means being able to think whatever
you want. People in jail can think whatever they
want. Thus they are free and should quit
complaining about how unfree they are.
amphiboly
Last night I shot an elephant in my pajamas.
How it got in my pajamas Ill never know.
accent
Obama: We should stop giving away free health
care to people who are unable to pay for it.
political opponent: Obama is now talking about
giving away free health care to people who are
unable to pay for it, and that is a direct quote.
composition
The military always follows orders. After all,
everyone in the military follows orders.
division
Neurons must be intelligent cells since the brain,
which is the organ most responsible for
intelligence, is made up of neurons.
fallacies of ambiguity
1. equivocation
2. amphiboly
3. accent
4. composition
5. division
fallacies
1. appeal to ignorance
2. appeal to illegitimate
authority
3. argument against the
person
4. appeal to emotion
5. appeal to pity
6. appeal to force
7. irrelevant appeal
8. complex question
9. false cause
10. begging the question
11. accident (stereotyping)
12. converse accident (hasty
generalization)
13. suppressed evidence
14. false dichtomy
15. equivocation
16. amphiboly
17. accent
18. composition
19. division

More Related Content

03 fallacies

  • 1. Fallacies how not to argue logically Elements of Logic Spring 2013 束anti-copyright: do what you want with this
  • 2. informal fallacies 1. fallacies of relevance These have in common the use of irrelevant information to try to persuade us into believing the conclusion. 2. fallacies of presumption These make additional unstated assumptions not warranted by the context. 3. fallacies of ambiguity These rest on the multiple meanings that often are attached to individual words and concepts.
  • 3. appeal to ignorance Nobody has ever proved that God exists, therefore God does not exist.
  • 4. appeal to ignorance There is no evidence of weapons of mass destruction in Iraq, thus there are really are no weapons of mass destruction in Iraq.
  • 5. appeal to (illegitimate) authority Lance Armstrong says that we should all do our part to cut carbon emissions, so we should do so.
  • 6. appeal to (illegitimate) authority Joe Camel says that smoking is good for you. Therefore, all of those stories about smoking being a health risk are wrong.
  • 7. argument against the person abusive ad hominem Rush Limbaugh is a big fat liar! That is why you should not pay any attention to his arguments.
  • 8. argument against the person circumstantial ad hominem Xandra is wearing a leather coat, calf-skin boots and a fur hat. So we can dismiss her arguments that animals should have rights.
  • 9. argument against the person tu quoque: Youre one too! Rush Limbaugh and his current wife have six divorces between the two of them. So we can dismiss his arguments about why marriage should be forever.
  • 10. appeal to emotion A world without God would be a cold and meaningless place, in which human lives have very little signi鍖cance. Therefore religious belief must have some basis in reality.
  • 11. appeal to pity I should not be held responsible for killing my wife. After all she was in bed with another man when I came home.
  • 12. appeal to force Either I get a good grade in this class or you are a dead man, professor.
  • 13. irrelevant appeal red herring I fail to see how helping out starving people in Africa is important. After all, there are plenty of hungry people right here at home.
  • 14. irrelevant appeal straw person Those baby killing Democrats are proposing more health care legislation. We can safely say that it should be opposed.
  • 15. irrelevant appeal non sequitur: It does not follow. The Patriots lost to the Ravens in the playo鍖s. Thus football is a really stupid sport.
  • 16. fallacies of relevance 1. appeal to ignorance 2. appeal to illegitimate authority 3. argument against the person 4. appeal to emotion 5. appeal to pity 6. appeal to force 7. irrelevant appeal
  • 17. complex question Have you stopped beating your kids?
  • 19. false cause post hoc ergo propter hoc after which therefore because of which Yesterday I had a cold, so I drank a bottle of whiskey. Now I feel better. Thus whiskey cures colds.
  • 20. begging the question You should be a Christian. If not, as the Bible suggests, you are going to end up in Hell.
  • 21. accident stereotyping Bridget is a woman. Thus she should not serve in combat positions in the military.
  • 22. accident genetic fallacy Biologists say we are descended from apes. But apes are dumb and we are smart, so those biologists must be wrong.
  • 23. converse accident (hasty generalization) That person from Massachussetts is a terrible driver. So beware of all people with Massachussetts plates on their car.
  • 24. suppressed evidence The shale gas boom is great for the economies of New York and Pennsylvania. After all there are lots of new jobs drilling for gas as a result.
  • 25. false dichotomy (false dilemma) Either you are in favor of attacking Iran or you are un-unpatriotic. Since you are not in favor of an attack, you must be un-patriotic.
  • 26. fallacies of presumption 1. complex question 2. false cause 3. begging the question 4. accident 5. converse accident (hasty generalization) 6. suppressed evidence 7. false dichotomy
  • 27. equivocation Being free means being able to think whatever you want. People in jail can think whatever they want. Thus they are free and should quit complaining about how unfree they are.
  • 28. amphiboly Last night I shot an elephant in my pajamas. How it got in my pajamas Ill never know.
  • 29. accent Obama: We should stop giving away free health care to people who are unable to pay for it. political opponent: Obama is now talking about giving away free health care to people who are unable to pay for it, and that is a direct quote.
  • 30. composition The military always follows orders. After all, everyone in the military follows orders.
  • 31. division Neurons must be intelligent cells since the brain, which is the organ most responsible for intelligence, is made up of neurons.
  • 32. fallacies of ambiguity 1. equivocation 2. amphiboly 3. accent 4. composition 5. division
  • 33. fallacies 1. appeal to ignorance 2. appeal to illegitimate authority 3. argument against the person 4. appeal to emotion 5. appeal to pity 6. appeal to force 7. irrelevant appeal 8. complex question 9. false cause 10. begging the question 11. accident (stereotyping) 12. converse accident (hasty generalization) 13. suppressed evidence 14. false dichtomy 15. equivocation 16. amphiboly 17. accent 18. composition 19. division