8/8/2019 POW1-Reasoning (Course 3)

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Valid and Invalid Reasoning and Reasoning in Advertising Name_________________________

VALID AND INVALID REASONING

You already know that affirming the hypothesis is a valid type of argument, while affirming the conclusion is

faulty. Two other types of arguments are denying the conclusion (a valid argument) and denying thehypothesis (a faulty argument). Consider the following:

If a person lives in Mexico, North American residents

then the person lives in North America

Mexicanresidents

VALIDARGUMENTS

AFFIRMING THE HYPOTHESIS

(original)

Mrs. Gonzales lives in Mexico.

Therefore, Mrs. Gonzales lives inNorth America.

PQP

Q

DENYING THE CONCLUSION

(contrapositive)

Mrs. Gonzales does not live in North America.

Therefore, Mrs. Gonzales does not live inMexico.

PQ~Q

~P

INVALID

ARGUMENTS

AFFIRMING THE CONCLUSION

(converse error)

Mrs. Gonzales lives in North America.

Therefore, Mrs. Gonzales lives in

Mexico.

PQ

Q

P

DENYING THE HYPOTHESIS

(inverse error)

Mrs. Gonzales does not live in Mexico.

Therefore, Mrs. Gonzales does not live in North

America.

PQ

~P

~Q

Write valid or invalid for each argument and name the type of argument.

1. If today is Sunday, then tomorrow is Monday.

Tomorrow is not Monday.Therefore, today is not Sunday.

2. If you live in Hawaii, you live on an island.

Marie lives on an island.Therefore, Marie lives in Hawaii.

3. If you wear Whiff Cologne, you will be noticed.Fred does not wear Whiff Cologne.

Therefore, Fred will not be noticed.

4. If you buy our product, we will give you a discount.Jill bought our product.

Therefore, we will give Jill a discount.

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Reasoning in Advertising

Argument 1: If you buy a GoGo Automobile, your neighbors will be jealous.Martina bought a GoGo.

Therefore, her neighbors are jealous.

This argument is logical, but its premise, "If you buy a GoGo Automobile, your neighbors will be jealous"may not be true.

Argument 2: If you wear Odor Sublime Perfume, you will be rich and famous.

Lillie von Loopo is rich and famous.Therefore, Lillie wears Odor Sublime.

This argument is not logical. It is a converse error or affirming the conclusion.

Most advertisers are more subtle. They may not state the original "ifthen" statement. They want you to

assume that the hidden statement is true. For example, an advertisement might show a young person being

invited to join a volleyball game. The ad might simply say "Use Terrific Tanning Lotion." The advertiserwants you to make the assumption that "If I use Terrific, I will never be left out."

You are to complete the project described below. Please note the warning in step 8.

CONDITIONAL STATEMENTS IN ADS

DUE __________________

1. Find an ad in a newspaper or magazine that has a conditional statement written in it or has one implied(photocopies not acceptable). (35 points)

2. Neatly cut out the ad and tape or glue it to a full sheet of paper. (10 points)

3. On another full sheet of paper, write the conditional statement in if-then form. (10 points)

4. Underline the hypothesis and circle the conclusion. (10 points)

5. Write the converse, inverse, and contrapositive of the if-then statement. Identify which is which. (30

points)

6. At the top of the page containing your sentences, write you name, your teacher's name, and the class

period. (3 points)

7. Staple the two sheets of paper together with the sentences on top. (2 points)

8. Have your papers ready to turn in at the beginning of class on the due date. You will not have classtime to cut, past/tape, write or staple.