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Summary of Informal Fallacies Defined with Examples



Key to the Argument Structures

L = Locutor, the person talking
p, s = statements
x, y = events, circumstances


1. Ad Ignorantiam (argument from ignorance)

p is unproved
—————        
Not p is true
OR Not p is unproved.
———————
p is true.

E.g., There is absolutely no evidence to suggest that you won’t do well in logic; therefore, we may conclude that you will do well.

or

E.g., There of no evidence to suggest that you will do well in logic; therefore we may safely conclude that you will not do well.




2. Ad Verecundiam (argument from authority)

Authority on x, L, says accept p.
p is outside the scope of subject x.
————————————––
p is true.

E.g., H. L. A. Jenkins, the noted international rose expert, has publicly stated that logic is essential to a life of excellence; surely such a renowned expert is trustworthy.




3. Complex Question

How (or why) is p true?
————————————–
p is true.

E.g., When are you going to stop fooling around and begin to take your education seriously? After all, your outlook on life will greatly improve when you cultivate consistent study habits.




4. Ad Hominem (argument against the person)

L says p.
L is a bad (good) person.
—————————–
p is false (true).

E.g., You can’t believe what Professor Smith says about teacher’s salaries, because as a teacher himself, naturally he would be in favor of higher earnings.




5. Accident

Rule or general statement p is true in circumstances x.
——————————————–———————–
p is true in circumstance y.

E.g., The Fifteenth Amendment to the Constitution of the U.S. gives all citizens the right to vote, so that clearly implies children citizens have the right to vote.




6. Converse Accident (hasty generalization)

p is true in circumstance x.
———————————
p is true in more general circumstance y.

E.g., Not one person spoke to me on the way to the Library; so it's clear to me that Lander University is not as friendly as I was led to believe.




7. False Cause

x is related to (or is followed by) y
————————————–—
x caused y.

E.g., Since Mary sat in the back of the class and made an A on the last test, maybe I should sit there too.

or

E.g., Napoleon became a great emperor since he was so short.




8. Petitio Principii (circular argument)

p is true.
q is true.
r is true.
———–
p is true
OR

p is true.
———–
It is not the case that not p is true.

E.g., Logic is an essential course because it is required at many colleges. It is required because the ability to reason is vital, and it is vital because logic is essential.




 9. Ad Populum (argument from popular appeal)

Snob Appeal:  

L says p.
L is in the elite.
---------------------
p is true.

OR Bandwagon:

The majority believe p.
-----------------------
p is true.

E.g., Snob Appeal: Since you have chosen to live the good life and a life of distinction, you deserve Four Roses Furniture in your home to show your elevated station.

E.g., Bandwagon: This logic course must be a good course because most people say so.




10. Ad Misericordiam (argument from pity or misery)

L says p.
L deserves pity because of x.
———————————
p is true.

E.g., Mary will be heartbroken if she does not get an A in logic; therefore, she deserves an A in order to spare her from personal disappointment.




11. Ignoratio Elenchi (irrelevant conclusion)

E.g., There is little point in taking a logic course because you'll never get much money out of it.

Note: Today, ignoratio elenchi is often termed a non sequitur (any argument where the conclusion does not logically follow from the premises). Since informal fallacies are not formally identifiable, no complete standard classification of the ways people can make mistakes in arguments is possible.

Thus, this category of informal fallacy is a "catch all" type. So, if a fallacy of relevance does not clearly fit into one of the common fallacies described above, it can be identified as this fallacy.


 
      

 
   

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