Chapter 9, Inference to the Best Explanation and from Analogy Video Solutions, Cengage Advantage Books: Understanding Arguments: An Introduction to Informal Logic

Problem 1

Imagine that you offer an explanation, and a critic responds in the following way. Which virtue (explanatoriness, depth, power, falsifiability, modesty, simplicity, or conservativeness) is your critic claiming that your explanation lacks?
1. But that won't explain anything other than this particular case.
2. But that conflicts with everything we know about biology.
3. But you don't have to claim all of that in order to explain what we see.
4. But that just raises new questions that you need to answer.
5. But that explains only a small part of the story.
6. But that would apply whatever happened.

Joanna Quigley

Numerade Educator

Problem 2

For each of the following explanations, specify which standard of a good explanation, if any, it violates. The standards require that a good explanation be explanatory, deep, powerful, falsifiable, modest, simple, and conservative. A single explanation might violate more than one standard.
1. Although we usually have class at this time in this room, I don't see anybody in the classroom, because a wicked witch made them all invisible.
2. Although we usually have class at this time in this room, I don't see anybody in the classroom, because they all decided to skip class today.
3. Although we usually have class at this time in this room, I don't see anybody in the classroom, because it's Columbus Day.
4. My house fell down, because it was painted red.
5. My house fell down, because of a powerful earthquake centered on my property that did not affect anything or anybody else.
6. My house fell down, because its boards were struck by a new kind of subatomic particle.
7. Although I fished here all day, I didn't catch any fish, because there are no fish in this whole river.
8. Although I fished here all day, I didn't catch any fish, because the river gods don't like me.
9. Although I fished here all day, I didn't catch any fish, because I was unlucky today.
10. That light far up in the night sky is moving quickly, because it is the daily United Airlines flight from Boston to Los Angeles.
11. That light far up in the night sky is moving quickly, because it is an alien space ship.
12. That light far up in the night sky looks like it is moving quickly, because there's something wrong with my eyes right now.

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Problem 3

Give two competing hypotheses that might be offered to explain each of the following phenomena. Which of these hypotheses is better? Why?
1. You follow a recipe carefully, but the bread never rises.
2. Your house begins to shake so violently that pictures fall off your walls.
3. Your key will not open the door of your house.
4. People start putting television cameras on your lawn, and a man with a big smile comes walking up your driveway.
5. Virtually all of the food in markets has suddenly sold out.
6. You put on a shirt and notice that there is no pocket on the front like there used to be.
7. A cave is found containing the bones of both prehistoric humans and now-extinct predators.
8. A cave is found containing the bones of both prehistoric humans and now-extinct herbivores.
9. After being visited by lobbyists for cigarette producers, your senator votes in favor of tobacco price supports, although he opposed them before.
10. Large, mysterious patterns of flattened wheat appear in the fields of Britain. (Some people attribute these patterns to visitors from another planet.)
11. A palm reader foretells that something wonderful will happen to you soon, and it does.
12. A neighbor sprinkles purple powder on his lawn to keep away tigers, and, sure enough, no tigers show up on his lawn.

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Problem 4

For each of the following arguments, state whether the indicated changes would make the argument weaker or stronger, and explain why. The strength of the argument might not be affected at all. If so, say why it is not affected.
1. My friend and I have seen many movies together, and we have always agreed on whether they are good or bad. My friend liked the movie trilogy The Lord of the Rings. So I probably will like it as well.

Would this argument be weaker or stronger if:
a. The only movies that my friend and I have watched together are comedies, and The Lord of the Rings is not a comedy.
b. My friend and I have seen very many, very different movies together.
c. My friend and I always watched movies together on Wednesdays, but my friend watched The Lord of the Rings on a weekend.
d. The conclusion claims that I definitely will like The Lord of the Rings a lot.
e. The conclusion claims that I probably won't totally dislike The Lord of the Rings.
2. All the students from Joe's high school with high grades and high board scores did well in college. Joe also had high grades and board scores. So he will probably do well in college.
Would this argument be weaker or stronger if:
a. The other students worked hard, but Joe's good grades came easily to him, so he never learned to work hard.
b. Joe is going to a different college than the students with whom he is being compared.
c. Joe plans to major in some easy subject, but the other students were pre-med.
d. Joe recently started taking drugs on a regular basis.
e. Joe needs to work full-time to pay his college expenses, but the others had their expenses paid by their parents.
3. A new drug cures a serious disease in rats. Rats are similar to humans in many respects. Therefore, the drug will probably cure the same disease in humans.

Would this argument be weaker or stronger if:
a. The disease affects the liver, and rat livers are very similar to human livers.
b. The drug does not cure this disease in cats.
c. The drug has to be injected into the rat's tail to be effective (that is, it does not work if it is injected anywhere else in the rat).
d. No drug of this general type has been used on humans before.
e. The effects of the drug are enhanced by eating cooked foods.

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Problem 5

EXERCISE V

Using the criteria mentioned above, evaluate each of the following arguments as strong or weak. Explain your answers. Be sure to specify the properties on which the analogy is based, as well as any background beliefs on which your evaluation depends.
1. This landscape by Cézanne is beautiful. He did another painting of a similar scene around the same time. So it is probably beautiful, too.
2. My aunt had a Siamese cat that bit me, so this Siamese cat will probably bite me, too.
3. The students I know who took this course last year got grades of A. I am a lot like them, since I am also smart and hardworking; and the course this year covers very similar material. So I will probably get an $A$.
4. This politician was caught cheating in his marriage, and he will have to face similarly strong temptations in his public duties, so he will probably cheat in political life as well.
5. A very high minimum wage led to increased unemployment in one country. That country's economy is similar to the economy in a different country. So a very high minimum wage will probably lead to increased unemployment in the other country as well.
6. I feel pain when someone hits me hard on the head with a baseball bat. Your body is a lot like mine. So you would probably feel pain if I hit you hard on the head with a baseball bat. (This is related to the so-called Problem of Other Minds.)
7. It is immoral for a doctor to lie to a patient about a test result, even if the doctor thinks that lying is in the patient's best interest. We know this because even doctors would agree that it would be morally wrong for a financial adviser to lie to them about a potential investment, even if the financial advisor thinks that this lie is in the doctor's best interests.
8. Chrysler was held legally liable for damages due to defects in the suspension of its Corvair. The defects in the Pinto gas tank caused injuries that were just as serious. Thus, Ford should also be held legally liable for damages due to those defects.

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