Question

Identify each fallacy and explain why it is that fallacy or give reason why it is a fallacy;

1. My son thinks Galaxies are better than iPhone, and he should know since he is a teenager.

2. I'm putting my money in a Vanguard account. My history teacher thinks the firm has the best mutual funds, and he is a smart man.

3. Given the right circumstances, humans will always revert to savages. Look at Nazis.

4. My student evaluations were better this year. I'll bet it's because I had to cancel class two times.

5. Global warming is not caused by human activity and the latest polls show the majority of Americans agree.

6. Just after I started doing yoga in the mornings, my golf swing improved. Yoga lowered my score!

7. Over the long haul, Obamacare will cut medical expenses. Informed people all say that.

8. I didn't pray hard enough. That's why my prayers weren't answered.

9.Sex before marriage is the road to perdition. You will end up in hell.

10. Whenever I go to Kroger I'm hungry; do you suppose going to Kroger makes me hungry?

Answer 1

Fallacy is a kind of defect in reasoning or some form of incorrect reasoning that lead to invalid arguments.

It is basically of two kinds: 1) Formal Fallacy 2) Informal Fallacy

1) Formal Fallacy

This form of fallacy arises due to defects in the form of arguments. The reasoning might seem correct but logically it is incorrect. Consider the following example:

Premise 1: If someone is allergic to peanut butter, then she doesn't eat peanut butter.

Premise 2: Maria doesn't eat peanut butter.

Conclusion: Therefore, Maria is allergic to peanut butter.

The conclusion here is invalid. If Maria is not eating peanut butter then it is not necessary that she is allergic to peanut butter ( she might just don't like peanut butter).

This has the form: (p->q) and q are true, then p is true. But according to the rules of inference, we know that we cannot determine the truth value of p from the given arguments.

This type of incorrect reasoning is called fallacy of affirming the consequent.

2) Informal Fallacy

This form of fallacy arises out of defects in the contents of arguments; not out of the form of arguments. Consider the following example:

  Premise 1: A feather is light.

Premise 2: What is light can't be dark.

Conclusion: Therefore, a feather can't be dark.

The conclusion here is invalid. The contents of both arguments refer to two different things. Premise 1 talks about light (weight), but premise 2 talks about light (colour). Thus, we can in no way make a comparison between the two and thus, the conclusion is invalid.

This type of incorrect reasoning is called fallacy of convocation.

Now, let us see the statements given in the question. (P1= Premise 1,P2= Premise 2, C= Conclusion)

1. P1: My son thinks Galaxies are better than iPhone.

P2: He is a teenager.

C: Therefore, he should know this.

This is an informal fallacy. The contents of the two given arguments are incomparable, and thus making a conclusion is invalid.

2. P1:  My history teacher thinks that this firm has the best mutual funds

P2: My history teacher is a smart man.

C: Therefore, I'm putting my money in a Vanguard account.

This is a formal fallacy. The smartness of history teacher in no way can guarantee that he always has the correct opinion in all the matters.

3. P1: If circumstances are right, humans will always revert to savages.

P2: Nazis reverted to savage ( Hitler)

C: Therefore, the circumstances were right when Nazis reverted to savage.

This is a formal fallacy. The fact that Nazis reverted to Hilter(savage) doesn't imply that the circumstances were right at that time.

4. P1: I had to cancel class two times

P2: My student evaluations were better this year

C: I will bet that the evaluations were better.

This is an informal fallacy. Cancellation of classes has no relation with the betterment of student evaluations.

5. P1: Results of latest polls imply that majority of Americans agree that global warming is not caused by human
activity.
C: Therefore, global warming is not caused by human activity.
This is a fallacy. Opinions of Americans can't be accorded for a global issue.

6. P1: I started doing yoga in the mornings.

P2: My golf swing improved.

C: Therefore, yoga lowered my score.

This is an informal fallacy. Lowering of scores has no relation with doing yoga in the mornings.

7. P1: There has been a long haul over the issue of medical expenses.

P2: All informed people say that medical expenses will be cut.

C: Therefore, Obamacare will cut medical expenses.

This is a formal fallacy. Obamacare may or may not cut medical expenses, we can never be 100% sure from the given premises about the decision of Obamacare.

8. P1: I didn't pray hard enough.

C: Therefore, my prayers were not answered.

This is a fallacy. We cannot logically prove the conclusion based on the given premise. ( Some prayers are not answered even on praying too hard )

9. P1: Sex before marriage is the road to perdition.

C: Therefore, you will end up in hell.

This is a fallacy. A person might end up in hell due to other sinful acts (according to one's religion) as well. Thus, premise doesn't strongly affirm the conclusion.

10. P1: If I go to Kroger, then I am hungry.

C: Therefore, going to Kroger makes me hungry.

This is a fallacy. P1 is of the form p -> q and C is of the form q -> p. And we know that p -> q is not equal to q -> p.