Critical Thinking – Fallacy


Part 2 of EXAM:  

I’m highlighting things in Red that I am sure are on the FINAL EXAM.   FALLACY TO UNDERSTAND ON TEST:   (Read the instructions of the Final Exam carefully, it should provide this description so you do not have to memorize it!)  

AFFIRMING THE CONSEQUENT: An invalid form of the conditional argument. In this case, the second premise affirms the consequent of the first premise and the conclusion affirms the antecedent.  

DENYING THE ANTECEDENT: An invalid form of the conditional argument. In this one, the second premise denies the antecedent of the first premise, and the conclusion denies the consequent.  

In the Final Exam instructions, it will explain invalid and valid arguments.  Make yourself a Chart to refer to when solving your

HPOTHETICAL SYLLOGISMS:  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent)    

Basic Pattern of Hypothetical Syllogisms  

If P, then Q    

If Q, then R

Therefore, if P, then R.  

*The “if” statement is called the antecedent. *The “then” statement is called the consequent.  

Patterns for Hypothetical Syllogisms *Affirming the Antecedent (Look at chart- a.k.a. AA)

If P, then Q.

P

Therefore, Q.

Example:  

If the stock market falls, then it will be a thin Christmas.

The stock market fell.

Therefore, it will be a thin Christmas.  

 Let’s walk through this.  

The antecedent (the “if” statement) is if the stock market falls. The consequent (the “then” statement) is it will be a thin Christmas.   So now we must figure out the Real Time Event.    The Real Time Event is that the stock market fell.   So what does that do?  The stock market fell agrees with the Antecedent (If the stock market falls).    You do not need to think about line 3….don’t even try to make sense of the argument by figuring in line 3….because line 3 does not matter!!!   This Example is VALID Because (look at the chart) it does the AA which means it AFIRMS THE ANTECEDENT.  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent)    

Remember, it is not enough to know if a Hypothetical Argument is valid or invalid, you must also know HOW…..make a chart out of the EXAMS instructions that explain what is valid and how, what is not valid and how and use it through this segment! 

Here is the other Valid Pattern for a Hypothetical Syllogism argument is:   DENYING THE CONSEQUENT  

If P, then Q.

Not Q.

Therefore, Not P.  

EXAMPLE:  

If I am poor, then I am not happy.

I am happy.

Therefore, I am not poor.  

Let’s walk through this.   What is the Antecedent? It is “if I am poor.” What is the Consequent? It is “then I am not happy.”   What is the Real Time Event? The Real Time Event is: I am happy.   What does that do?  I am Happy is opposite of the “then I am not happy.” So what does that mean?  It means: We are: Denying the Consequent. REMEMBER DO NOT LOOK AT LINE 3, IT DOES NOT MATTER!!! Look at the chart.  Where does Denying the Consequent fall under?  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent) 

This Hypothetical Syllogism is: VALID Because:  It falls under Denying the Consequent.  

Here is another pattern of a Hypothetical Syllogism:   *DENYING THE ANTECEDENT  

If P, then Q.

Not P.

Therefore, not Q.  

EXAMPLE:  

If the sun dies, the earth will become barren.

The sun did not die.

Therefore, the earth is not barren.

Let’s break it down.   What is the Antecedent? It is: If the sun dies. What is the Consequent? It is: the earth will become barren. What is the Real Time event?  It is: The sun did not die.   DO NOT LOOK AT LINE THREE….IT DOES NOT MATTER!   So if the sun did not die, what does that mean?  Look at the Antecedent.  It says “If the sun dies.”  But the real time event says the sun did not die…..what does that do? Look at the chart!  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent) 

That is: Denying the Antecedent….. And that is INVALID, because it is in the INVALID instruction box.  When the antecedent is denied it is an invalid argument.  Remember you do not have to remember these rules, just take the instructions out of the EXAM explanation before the problems and make this chart.  When you break down the examples on the test, you can look at it to figure out what each example is doing. 

Always know:

The Antecedent is the IF statement.                          

The Consequent is the THEN statement.                         

The REAL TIME event does what?                          

Ignore the last line….it does not matter w/ Hypothetical Syllogisms!  

The Last Pattern:  

AFFIRMING THE CONSEQUENT  

If P, then Q.

Q.

Therefore, P.  

EXAMPLE:  

If I walk to the store, then I will be tired this evening.

I am tired this evening.

Therefore, I walked to the store.  

Let’s break it down.  

The Antecedent is: if I walk to the store. The Consequent is: then I will be tired this evening. The Real Time event is: I am tired this evening.   Ignore line 3.   I am tired this evening agrees with the Consequent, I will be tired this evening.   So what does that mean?  Look at the chart. 

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent) 

I am tired this evening affirms I will be tired this evening…. It is   INVALID   And it is Invalid because it is: Affirming the Consequent, which is found in the chart above!   Fredericka says:  Read Left to Right, Top to bottom, what happens in Real time?  Don’t try to agree or disagree with the argument, just see if it is a valid or invalid argument and know why.  Analyze and follow the flow of the argument.  It is important that you can break down the argument.   And I say….ignore the last line, it is not important to the pattern to figure out what is happening with a Hypothetical Syllogism problem only!  

EXAMPLE:  

If he wants to get that job,

then he must know Spanish.

He knows Spanish, so the job is his.  

What is the Antecedent:  if he wants to get that job. What is the Consequent: then he must know Spanish. What is the Real Time event: he knows Spanish. What do we ignore: so the job is his.   He knows Spanish agrees with the Consequent he must know Spanish. Look at the chart:  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent) 

THIS EXAMPLE IS: 

INVALID BECAUSE: It is Affirming the Consequent!    

EXAMPLE:  

If she qualifies for a promotion, she must speak English.

She doesn’t qualify for the promotion,

so she must not know how to speak English.  

Let’s break it down.  

The Antecedent: if she qualifies for a promotion. The Consequent: “then” she must speak English. The Real Time Event: She doesn’t qualify for the promotion.   So the Real Time Event she doesn’t qualify for the promotion disagrees with the antecedent she qualifies for a promotion.    Look at the chart:  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent) 

This is: Denying the Antecedent, therefore, it is an INVALID example.   EXAMPLE:  

Chris and Nick would be very happy if the Browns beat the Steelers.

The Browns did beat the Steelers,

so Chris and Nick are very happy indeed.

What is the Antecedent: if the Browns beat the Steelers. What is the Consequent: “then” Chris and Nick would be very happy. What is the Real Time Event: the Browns did beat the Steelers Ignore that Chris & Nick are indeed very happy, that does not matter.   The real time event of the Browns beating the Steelers agrees with the Antecedent if the Browns beat the Steelers.  This is a positive form.  Therefore, look at the Chart.  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent) 

What is happening? It is Affirming the Antecedent…. Therefore this Example is   VALID  

EXAMPLE  

Roberto thought that if he worked very hard, his boss would give him a raise or a promotion.

He made sure she noticed him, but she did not give him a raise or promotion.

He thought he must not have worked hard enough.  

Let’s walk through it.   The IF statement (Antecedent): if he worked very hard The THEN statement (Consequent): his boss would give him a raise or promotion.   Ignore all extra information and look for the REAL TIME EVENT: She did not give him a raise or promotion.   She did not give him a raise or promotion IS NEGATIVE to his boss would give him a raise or promotion.   Look at the chart:  

VALID_­___________________INVALID 

AA                                                                    DA

(affirm antecedent)                 (Denying the antecedent)  

DC                                                                      AC

(Denying the consequent)    (Affirming the consequent) 

 This real time event is Denying the Then event the Consequent:   Therefore this argument is:   VALID  

ANSWER THESE BY CIRCLING VALID OR INVALID/ MAKE A REASON WHY FROM THE CHART (I will send answers later)  

  1. Madeline must have known the material for the test, because if a person knows the material, that person will get an A, and Madeline was one of the students that got an A.

  VALID  OR   INVALID WHY:_________________

  1. “I’m still eating too much ice cream,” lamented George. “My waist measurement is the same as it was six months ago. I know if I didn’t eat so much ice cream, I would reduce my waist size.”

  VALID   OR   INVALID  WHY: ­­­­­­­­­­­­­­____________  

  1. The best way to make sure we pay fewer taxes is to elect conservatives. We must not have elected enough conservatives, because we are paying more taxes.

  VALID   OR   INVALID    WHY: _____________  

  1. If my neighbor were a decent human being, he wouldn’t let his yard trash fall onto my property. But he’s not a decent human being, so we get to clean his trash as well as ours.

    VALID   OR   INVALID    WHY: _____________

  1. Anastasia believes that if she treats people honestly and with an open mind, she will have diverse friendships.  She is honest and open-minded and has friends all over the world.

  VALID  OR   INVALID     WHY: ___________________  

  1. If I could understand the concept of hypothetical syllogisms, I would get a passing grade. Hurray! I got a passing grade, so I must have understood the concept of hypothetical syllogisms.

  VALID   OR   INVALID     WHY: _____________  

If I turn 40, I will go to Asia

I turned 40. Therefore,

I went to Asia.  

VALID   OR   INVALID     WHY: ________ 

If I turn 40, I will go to Asia.

I died at 39.

Therefore, my mom went to Asia.  

VALID   OR   INVALID     WHY: _______________ 

If I study hard, I will pass the exam.

I did not pass the exam.

Therefore, I did not study hard.  

VALID   OR   INVALID     WHY: ______________ 

If I study hard, I will pass the exam.

I passed the exam.

Therefore, I studied hard.  

VALID   OR   INVALID     WHY: __________  

  1. If he turns 40, he will go to Europe.

He turned 40, and went to Europe.   VALID   OR   INVALID     WHY: ______________________________  

  1. If the Braves win the World Series, I will win $1000.00.

The Braves were shut-out. I did no win the money.   VALID   OR   INVALID     WHY: ______________________________

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Published in: on September 25, 2009 at 10:39 PM  Comments (1)  

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  1. Blecher’s letter goes on to identify two basic legal defenses for Sterling.


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