Summary of Informal Fallacies

See http://philosophy.lander.edu/logic/fallacy_topics.html for detailed explanations.

Symbol	Meaning
L $=$	Locutor, speaker
s $=$	statements, propositions
x,y $=$	events, circumstances

1. Ad ignorantiam (argument from ignorance)
   

   p is unproved.	or	Not p is unproved.
   Not p is true.		p is true.

   
   
   

   E.g., There is absolutely no evidence to suggest that you won't do well in logic; thus, we may conclude that you will do well. OR E.g., There is no evidence to suggest that you will do well in logic; thus, we may safely conclude that you will not do well.

2. Ad verecundiam (argument from authority)
   

   Authority on x, L, says p is true.

   p is outside of 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; consequently, this view must be so.

3. Ad hominem (argument against the person)
   

   L says p.		L says p.
   L is a bad (good) person.	or	L comes from bad (good) x, y.
   p is false (true).		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 more money. OR E.g., You can't believe what Professor Smith says about teacher's salaries because he comes from a family of mostly teachers; naturally, he would be in favor of a higher salary.

4. Ad populum (argument from popular appeal)

   Snob Appeal		Bandwagon
   People in the elite believe p	or	The majority believe p
   p is true.		p is true.

   
   
   

   E.g., Snob Appeal: You have chosen the good life and a life of distinction, so now you need Four Roses Furniture to show that you have arrived. OR E.g., Bandwagon: This logic course must be a good course because most people believe it is.

5. Ad misericordiam (argument from pity or misery)

   L says p. L deserves pity because of x,y.

   p is true.

   
   
   

   E.g., Mary should be given the lead part in the play because she will be broken-hearted if she does not get the role.

6. Ad baculum (argument from force)

   L says accept p or event x will happen.

   x is bad (or good).

   p should be accepted as true.

   
   
   

   E.g., I'm sure you will agree to the proposal before your committee because your future with this company might end if you don't.

7. 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 college education seriously? You will only benefit yourself if you start studying effectively.

8. False Cause

   non causa pro causa		post hoc ergo propter hoc
   x is related to y.	or	x is followed by y.
   x caused y.		x caused y.

   
   
   

   E.g., Napoleon became a great emperor since he was so short. OR E.g., Since Jack sat in the back of the class and made an A on the last test, maybe I should sit there too.

9. Petitio Principii (circular argument; begging the question)

   p is true.
   q is true.	or
   r is true.		p is true.
   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 at those colleges because the ability to reason is vital, and it is vital because logic is so essential.

10. Accident (ceteris paribus exceptions)

    Rule or general statement p is true in circumstance x.

    p is true in irrelevant circumstance y.

    
    
    

    E.g., Since the United States is a democracy all persons all persons should be allowed to vote. Therefore, children ought to be able to vote for President.

11. Converse Accident (hasty generalization; glittering generality)

    p is true in circumstance x.

    p is true in all or most circumstances.

    
    
    

    E.g., Not one person spoke to me on the way to the library; Lander University is not as friendly as I was led to believe.

12. Ignoratio elenchi (non sequitur; irrelevant conclusion)

    There is no complete standard classification of the ways people can make mistakes in arguments. Ignoratio elenchi is sometimes considered a suitable paraphrase for ``fallacy.'' We use the term for any irrelevant argument given, whether valid or invalid.