Informal Fallacies: Fallacy Fest!

FALLACY FEST!!!!

1. Bad/DA

2. Bad/AC

3. Appeal to Authority

4. Fallacy of Equivocation

5. Hasty Generalization

6. Ad Baculum (Appeal to Force)

7. Red Herring

8. Appeal to Authority

9. Ad Hominem

10. Ad Misercordiam (Appeal to Pity)

11. Begging the Question

12. Straw Man

13. Complex Question

14. Internet Fallacy



Identify the (Bad) Reasoning Fallacy then Create 1 Example of Your Own

Concept 1:

A: Person 1: Everything in life happens for a reason...maaaaaaaaaaaaaaaan. There's a greater purpose to everything.

Person 2: That's ridiculous. What's the reason for my moving my finger right now?

Person 1: Because you had the thought "move your finger" which caused the nerves leading to your finger to fire in succession, culminating in the movement of your finger...duh.


B: Science has discovered many laws of nature. This surely constitutes proof that there is a God, for wherever there are laws, there must be a lawgiver. Consequentially, God must exist as the great lawgiver of the universe.


C: Since, as scientists tell us, energy neither comes into being nor goes out of being, there should be no energy crisis.









Fallacy of Equivocation: The fallacy of equivocation is when a key term in the argument isn't used with a consistent meaning throughout the premises and/or conclusion. In other words, a term might be used differently between premises or between the premises and the conclusion.

Concept 2:

A: Why should I believe what he says about our economy? He's not even a citizen!


B: You can't accept her advice. She is so old she has no idea what goes on in today's world.


C: Why would you listen to him? He's too young to have any wisdom about life.


D*: Of course Senator X thinks my administration's tax proposals are bad for the country. After all, his political party lost the last election, and everyone knows that losers are jealous.


E*: You don't want cars to get better gas milage because you are a self-centered rich bastard who isn't affected by gas prices. All you care about it how big your engine is.


F*: Of course you think that people should take drugs. You work for a pharmaceutical company and you make more money if more people take drugs.













Explanation of Ad hominem (against the person): When a claim is rejected or judged to be false based on an alleged character flaw of the person making the claim. A second form occurs whenever someone's statement or reasoning is attacked by way of a stereotype, such as a racial, sexual, or religious stereotype. A third form involves the use of circumstances of a person's life to reject his claims. Exception: denying someone's claim by calling them a liar and they have a reputation for being one.

Concept 3

A. Vaccines cause autism. Didn't you hear the interviews with Robert DeNiro and Jenny McCarthy?


B. The Food Babe says GMOs cause cancer. There's no way I'm eating those franken foods!













Explanation of Argument from Authority: Appealing to an unqualified authority to support a position.

Concept 4:

A.













Non-sequitur: Literally "does not follow". When a premise is irrelevant to the conclusion.

Concept 5:

A. Conrad Hilton started out dirt poor and became super-rich, therefore anyone can do it.

B. About half of my friends at BGSU have student loans, therefore about half of BGSU students have student loans.

C. Acupuncture helped my back feel better, it must work.












Hasty Generalization: Moving from a small (likely unrepresentative sample) to a generalization.

Concept 6:

A.

B. Last night my mom got mad at me, then my dog got sick. Can you change my grade from a C to a B?
















Appeal to Pity (Ad Misercordiam): Arguing for a claim by appealing to pity.

Concept 7:

A: If you don't get rid of your suspected chemical weapons we will bomb you.

B: If you don't do your homework, I will judo chop you.














Appeal to Force (Ad Baculum): When the arguer essentially presents a threat of force instead of a reason for accepting a position.

Concept 8:

A. Person A: Given the tragic nature of mass shootings, we should consider implementing some sort of background check to make sure people buying guys don't have any known major psychological problems or any records of violent criminal behavior.

Person B: My opponent doesn't think people have the right to own guns. In person A's world, citizen's won't be able to lawfully defend themselves or even go hunting.







B. Person A: If you deny people the right to self-defense then you are risking increasing the rate home break-ins because a major deterrent will have been removed.

Person B: My opponent thinks we should give children AK-47s for self-protection when their parents aren't home. This is obviously a bad idea.













Straw Man: The opposing view is distorted and exaggerated so it can easily be defeated.

Concept 9:

A. (From the Washington Post)
BLM contends that Bundy owes $1 million in fees, and will also have to pay the round-up expenses. Bundy — who retorts that he only owes $300,000 in fees — says the city folk are only hurting themselves by taking his cows. He told a reporter from the Las Vegas Review Journal that there would be 500,000 fewer hamburgers per year after his cows were towed away; “But nobody is thinking about that. Why would they? They’re all thinking about the desert tortoise. Hey, the tortoise is a fine creature. I like him. I have no problem with him. But taking another man’s cattle? It just doesn’t seem right.”




B. How could anyone think GMOs are safe? They're inserting fish genes into tomatoes!!!!!111!!!1111!!! It just ain't natural!!!!11!!!!11!!













Red Herring Structure:

Topic A is under discussion.
Topic B is introduced as though it is relevant to topic A.
Topic B ends up being discussed, leaving topic A unresolved.

Concept 10:

A. Celibacy is an unnatural and unhealthy practice, since it is neither natural nor healthy to exclude sexual activity from one's life.

B. Thoughts are not part of the physical world, since thoughts are in their nature non-physical.

C. Happiness is the highest good for a human being, since all other values are inferior to it.
















Begging the Question: When you assume your conclusion, implicitly or explicitly, in your premises. That is, your premises already assume they very thing you're trying to prove.

Concept 11:

A. Are you going to admit that you're wrong?

B. When should I expect your apology?

C. Why do you hate America?

D. When are you going to stop drinking and grading?














Complex Question: When a question assumes only one possible answer.

Review for Test 3: MP, MT, CP, vI, DS, &I, &E, RA

Agenda

1. Office Hours: Monday after class Shatzle Hall Rm 314 (Seminar Room).
   Review Session: Wednesday at 4:30--You get it. 
2. Quiz
3. Questions about HW?
4. Mini Review of vI and DS
5. Practice for Test

Quiz
A.  Explain and give an example of the law of non-contradiction.
B.  Explain and give an example of the law of the excluded middle.
C. Translate:

1. If you're neither sure about how to do CP nor RA then you shouldn't go OUT and skip STUDYING.
2. You shouldn't watch CAT videos or and CUTE animal videos unless you've finished STUDYING. 

D. 

1. (Rv~S)>(T&~U)
2. (T&Q)>P        /:.  (P>~Q)>~(R&Q)

Translations

Mnemonics for conditional translations:
If P then Q; Q if P = P>Q. Rule: Whatever immediately follows the 'if' comes first.
P only if Q; Only if Q, P = ~Q>~P. Rule: Whatever follows 'only if' is negated then put first, the other proposition is negated and put after the '>'.
Unless P, Q; Q unless P = ~P>Q. Rule: Whatever follows 'unless' is negated and put first. Think of 'unless' as 'if not P'.
Other mnemonics:
Neither P nor Q= (~P&~Q)
P or Q but not both=(PvQ)&~(P&Q)

Practice
A. Unless you bring me either peanut butter COOKIES or DONUTS you won't get any BONUS points.
B. You can borrow the CAR only if you neither DRINK nor SMOKE.
C. Only if you start SQUATTING and DIETING now will you be ready for BEACH season.
D. If neither BOB nor GEORGE will help then I'll have to ask MARY or JERRY but I don't want to have to ask MARY.
E. If I survive the last WEEKS of this semester then I'm going to spend a week camping in the ROCKIES unless it RAINS or SNOWS.


Proofs: RA, CP, MP, MT, &I, &E, vI, DS, <>I, <>E
A.

1. /:. (P&~Q)>(Pv(S&T))

B. 

1. A
2. (~BvD)>F
3. ~(Dv~F)>~F
4. ~E>~C      /:.  (A>~B)>(C>~(D>~E))

C.

1. ~(Av~B)v(~CvD)
2. A&~D
3. ~(~C&A)vE    /:.  Ev(F>G)

D. 

1. /:.  (P>Q)<>(~Q>~P)

E*.  

1. /:.  ~(PvQ)<>(~P&~Q)

F. 

1. (RvP)>Q
2. (R>~S)>(Sv~Q)
3. ~P                        /:.  (R>~S)>~(RvP)

G. 

1. ~R
2. (~RvT)>(P>Q)    /:.  ~((P>Q)>~(~RvS))

H. 

1. ~(D&~B)v~A   /:.  A>(~B>(C>~(D&~B)))

More Reductio, Translations with 'v', Logical Equivalence

Agenda

1. Quiz
2. Questions about homework?
3. Law of non-contradiction and law of the excluded middle. 
4. Translating sentences with 'v'.
5. Logical Equivalence.
6. RA proofs.

Quiz
A. 

1. /:. (P&Q)>~(P>~Q)

B. 

1. Either you'll get this RIGHT or you won't unless CONTRADICTIONS are true.

2. You can have a sticker only if you either make no MISTAKES or bring me a COOKIE. 

Law of Non-Contradiction

Definition: The negation of a contradiction is always true.

Symbolized: ~(P&~P) = True

E.g., 

1. The fact that I'm both alive and not alive is false. This whole sentence is true.
2. The fact that the room is both empty and not empty is false. This whole sentence is true.
3. The fact that I like cookies and don't like cookies is false. This whole sentence is true.

The Law of the Excluded Middle

Definition: The assumption that any sentence is either true or false is always true.

Symbolized: Pv~P = True

E.g.,

1. Either I'm going to study or I'm not going to study. The whole sentence is true.
2. Either you are wearing pants or you are not wearing pants. This whole sentence is true.
3. Either Bob is here or he isn't here. This whole sentence is true. 

Translations with 'v'
A.

1. Either I'm not going to STUDY or I'm not going to WATCH  a movie. 
2. Unless you WORK hard you'll either make your MOTHER cry or your FATHER angry. 
3. You can have either COOKIES or DONUTS but you can't have both. (Careful!)
4. You can have either COOKIES or DONUTS or both.
5. You can have neither COOKIES nor DONUTS unless you HELP me. 
6. I would HIKE Death Valley only if either my BROTHER or JEREMY came with me.
7. You can have neither COOKIES nor DONUTS unless you EAT your dinner.

Logical Equivalence 

A. 

1. /:. (P>Q)<>(~Q>~P)

Reductio Proofs (left over from last week)

D. 

1. ~D>(A&C)
2. (B&D)>E
3. (DvF)>~E  /:. ~(A&C)>~(Bv~D)

E. 

1. (R&S)>~(P>~Q)
2. ~(T>P)>(R&S)
3. T
4. ((T>P)&P)>Q        /:. ~(P>Q)

F.

1. (~D&~E)>F
2. A&~D
3. ((F&~B)vG)>~(A>~B)    /:.  (A>~B)>~(Dv~E)

Reductio Rule (RA)

Agenda

1. Quiz
2. Questions about HW?
3. New Rule: RA
4. Proofs

Quiz

A. 

1. ~A&B
2. (~Av(B>~C))>(Dv~B)   /:. D

B. 

1. (Pv~Q)>R
2. P&S  /:.  ~(S>~R)

C. 

1. If you have only TWENTY % in the course you will GET an A only if you CHALLENGE and DEFEAT me in a judo death match, but if you WORK really hard you can still PASS.
2. I'm usually GRUMPY unless someone brings me either CHOCOLATE chip or PEANUT butter cookies.

Reductio (RA)

Solve:

1. ~Q&P  /:.  ~(P>Q)

How to set up an RA proof: Suppose I need to solve for ~(P>Q)

Step 1. Do all the top down rules you can.

Step 2. RA is a bottom up rule. We look at the last line of our proof that doesn't have a justification and we set up from there. Leave space and write the 'opposite' of the line you're trying to solve.

1.  ~Q&P    A

2. ~Q          &E 1

3. P             &E 1

4. P>Q      ARA

.

.

.

.

.

.

.

.

n. ~(P>Q)  RA

Step 3. Try to derive a contradiction by putting two 'opposites' together with &I

1.  ~Q&P    A

2. ~Q          &E 1

3. P             &E 1

4. P>Q       ARA

5. Q           MP 3, 4

6. Q&~Q   &I 2, 5

7. ~(P>Q)  RA 4, 6

RA Proofs
A.

1.  T>P
2.  (P&~Q)>~(S&~Q)  /:. (P>~Q)>~(T&S)

B.

1. ~P
2. (Pv~Q)>Q  /:. ~(Pv~Q)

C. 

1. D<>~(A&~B)
2. ~(D&C)v(A&~B)  /:.  ~(A&~B)>~(D>C)

D. 

1. ~D>(A&C)
2. (B&D)>E
3. (DvF)>~E  /:. ~(A&C)>~(Bv~D)

E. 

1. (R&S)>~(P>~Q)
2. ~(T>P)>(R&S)
3. T
4. ((T>P)&P)>Q        /:. ~(P>Q)

F.

1. (~D&~E)>F
2. A&~D
3. ((F&~B)vG)>~(A>~B)    /:.  (A>~B)>~(Dv~E)

Disjunctive Syllogism

Agenda

1. Exam: 
1. If you didn't do as well as you would have liked 
2. (a) what was your attendance record? Did you take advantage of office hours and review sessions?
3. (b) What percentage of the homework did you complete?
4. (c) What can I do to help? 
2. Disjunctive Syllogism and 'v' Introduction.
3. Proofs

Exam

Surprising Results!!!!

Students who scored less than 80% on the test also had 80% or lower attendance rates. The lower the score, the lower the attendance rate. It's almost as though the two are related...

1. If you didn't do as well as you would have liked: 
2. (a) what was your attendance record? Did you take advantage of office hours and review sessions?
3. (b) What percentage of the homework did you complete?
4. (c) What can I do to help? 

Disjunctive Syllogism 

Basic Rule: 

1. PvQ              A
2. ~P/~Q          A
3. Q/P              DS

In natural language: 

1. Either you want PIZZA or you want QUOLA.
2. You don't want PIZZA/You don't want QUOLA.
3. You want QUOLA/You want PIZZA.

Adding complexity (but same rule):

A.

1. (P&Q)v(P>Q)  A
2. ~(P>Q)             A
3. P&Q                 DS

B. 

1. ((A<>~B)>(C>~B))v~((~DvC)>(C<~~D))      A
2. what would I need in order to derive                A
3. ((A<>~B)>(C>~B))                                          DS

Fun Activity!!!

In your groups create at least two natural language arguments using DS then symbolize it.

'v' Introduction

Basic Rule:

A. 

1. P                                                  A
2. PvQ (where Q can be anything) v Int

B. Let's kick it up a notch....BAAAM!!

1. P                                        A
2. Pv(P<>((~Q>R)&(SvT))  vInt

In natural language:

1. I'm going to study LOGIC tonight.                 A
2. I'm going to study LOGIC tonight or I'm going to order a PIZZA, drink BEER, and WATCH Trailer Park Boys.                                                       vInt

Fun Activity!!!

In your groups create at least 2 vInt arguments in natural language then symbolize it.

Proofs

A. 

1. P
2. (PvQ)>R   /R

B. 

1. (A&B)
2. (C>E)>~((A&B)v(~C>D))   /:. (C>E)

C. 

1. (~P<>Q)&~R
2. (((~P<>Q)&~R)v(((~T&S)v~P>~T)<>((S&U)>V)v(~T<>R)))>P
3. P>Q                /:. Q

D. 

1. (A>B)v(~C&D)
2. ~(A>B)   /:.  ~C

Introduction to Biconditionals and Disjunctions

Agenda

1. Quiz
2. Biconditional Proofs

Quiz

A.

1. ~P>R
2. (P>~Q)>~R    
3. P>~Q     /:. P<>~Q

B. 

1. Unless you BRUSH your teeth and SHOWER you shouldn't WRESTLE with me.
2. If you neither did the HOMEWORK nor came to OFFICE hours you're going to have a BAD time.
3. You should PANIC only if you don't know how to do MODUS ponens and modus TOLLENS.

Setting Up Proofs with Biconditional (Biconditional Strategy)
You will use this method anytime a biconditional is the bottom line unjustified line of your proof. Think of <> as & for two >s. In other words, I going to have to do two proofs: one proof for one direction and one for the other.
Suppose you have to solve for P<>Q. P<>Q is logically equivalent to P>Q & Q>P. This means in order to prove P<>Q I'm going to have to do two proofs: one for P>Q and one for Q>P then I can put them together using <>Int.

Step 1: Write P<>Q at the bottom of your proof.

.
.
.
.
.
.
.
.
x. P<>Q

Step 2: I know that P<>Q is the same as P>Q and Q>P. Scan the given assumptions above to see if I'm given either of the conditionals. If I'm not given any then I'm going to set up two proofs: one for P>Q and one for Q>P. If one of the two conditionals is given to me in the assumptions then I only need to set up a proof for the conditional not given in the assumptions.

.
.
.
.
.
e. Q>P
.
.
.
.
m. P>Q
x. P<>Q        <>Int e, m

Step 3: Now that I've set up my proof I go about independently solving for both P>Q and Q>P beginning with CP as we've learned from previous lessons.

a.    Q    ACP
.
.
.
d.    P     ____
e. Q>P  CP a, d
f.    P    ACP
.
.
.
l.    Q  ____
m. P>Q  CP f, l
x. P<>Q  <>Int. e, m.


Proofs with <> + MP, MT, DN, &Int, &Elim, CP
A.

1. ~P>R
2. (P>~Q)>~R    
3. P>~Q     /:. P<>~Q

B.   

1. P&~Q  /:. P<>~Q

C. 

1. ~(C&~B)>~A    /:. (A&~B)<>A

D.

1. (S>R)&~R
2. (~S>Q)&P
3. P>R        /:.  (P&Q)<>(~S>R)

E. 

1. (C<>~D)&C
2. B<>~A      /:.  (A>~B)&(C&~D)

F. 

1. ~S>(~Q&R)
2. S>~(P>~Q)    /:.  ((P>~Q)&R)<>~S

Review: Proofs with MP, MT, &Int, &Elim, DN, and CP

Agenda

1. If you're having trouble with anything we've done so far please see me during office hours so I can help you. Shatzel Hall Rm 340, M&F after class. 
2. Quiz
3. Review of MP, MT, Denying the Antecedent, Affirming the Consequent.
4. Review of Translations.
5. Review of Proofs.

Quiz

A. Translate the argument, name the argument structure and say whether it's valid. If it's invalid, make it valid.

Argument 1

1.  If Jerry DRINKS too much he won't WAKE up for work on time.
2.  Jerry didn't WAKE up for work on time.
3.  Therefore, Jerry DRANK (translate same as DRINKS) too much. 

Argument 2

1.  Unless you're the JESUS of logic then you should PRACTICE a bit of logic every day and see AMI for help.
2.  You're not the JESUS of logic.
3.  You should PRACTICE a bit of logic every day and see AMI for help.

B. Proof

1. T>~S
2. (~T&P)>(Q>~R)  /:.  (S&P)>(Q>~R)

Review of MP, MT, Denying the Antecedent, and Affirming the Consequent

A. Construct a conditional argument and give that argument in each of the above formats.

Review of Translations

A. You'll get this RIGHT only if you STUDIED.

B. Unless you STUDIED you won't get this RIGHT.

C. If you get this RIGHT then you STUDIED.

D. If you don't get this RIGHT then you neither STUDIED nor UNDERSTOOD it, moreover you should be CONCERNED if you didn't get it RIGHT.

Do You Haz Proofs?

A.

1. (B&C)>A
2. ~(B&C)>(~D>C)
3. ~A>B
4. ~E>~B   /:. ~A>(~D>(C&E))

B. 

1. (~P&R)>T
2. S>~(Q&R)   /:.  (~P&Q)>(R>(~S&T))