Constructing Strong Inductive Arguments
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When you use inductive reasoning, your conclusion is only as strong as the evidence—the facts, details, or examples—
Generalization Too Broad
The conclusion you state cannot go beyond the scope of your evidence. Your evidence must support your generalization. For instance, you cannot survey just three international students in your school and conclude that the school does not go far enough to accommodate international students. To reach such a conclusion, you would have to consider a large number of international students.
Insufficient Evidence
The evidence on which you base an inductive conclusion must be representative, not atypical or biased. For example, you cannot conclude that students are satisfied with the course offerings at your school by sampling just first-
Irrelevant Evidence
Your evidence has to support your conclusion. If it does not, it is irrelevant. For example, if you assert that many adjunct faculty members make substantial contributions to your school, your supporting examples must be adjunct faculty, not tenured or junior faculty.
Exceptions to the Rule
There is always a chance that you will overlook an exception that may affect the strength of your conclusion. For example, not everyone who has a disability needs special accommodations, and not everyone who requires special accommodations needs the same services. For this reason, you should avoid using words like every, all, and always and instead use words like most, many, and usually.
EXERCISE 5.6
Read the following arguments, and decide whether each is a deductive argument or an inductive argument and write “D” or “I” on the lines below.
Freedom of speech is a central principle of our form of government. For this reason, students should be allowed to wear T-
shirts that call for the legalization of marijuana.________ 141
The Chevy Cruze Eco gets twenty-
seven miles a gallon in the city and forty- six miles a gallon on the highway. The Honda Accord gets twenty- seven miles a gallon in the city and thirty- six miles a gallon on the highway. Therefore, it makes more sense for me to buy the Chevy Cruze Eco.________ In Edgar Allan Poe’s short story “The Cask of Amontillado,” Montresor flatters Fortunato. He lures him to his vaults where he stores wine. Montresor then gets Fortunato drunk and chains him to the wall of a crypt. Finally, Montresor uncovers a pile of building material and walls up the entrance to the crypt. Clearly, Montresor has carefully planned to murder Fortunato for a very long time.________
All people should have the right to die with dignity. Garrett is a terminally ill patient, so he should have access to doctor-
assisted suicide.________ Last week, we found unacceptably high levels of pollution in the ocean. On Monday, we also found high levels of pollution. Today, we found even higher levels of pollution. We should close the ocean beaches to swimmers until we can find the source of this problem.________
EXERCISE 5.7
Read the following arguments. Then, decide whether they are deductive or inductive. If they are inductive arguments, evaluate their strength. If they are deductive arguments, evaluate their soundness.
The Farmer’s Almanac says that this winter will be very cold. The National Weather Service also predicts that this winter will be very cold. So, this should be a cold winter.
Many walled towns in Europe do not let people drive cars into their centers. San Gimignano is a walled town in Europe. It is likely that we will not be able to drive our car into its center.
The window at the back of the house is broken. There is a baseball on the floor. A few minutes ago, I saw two boys playing catch in a neighbor’s yard. They must have thrown the ball through the window.
Every time I go to the beach I get sunburned. I guess I should stop going to the beach.
All my instructors have advanced degrees. George Martin is one of my instructors. Therefore, George Martin has an advanced degree.
My last two boyfriends cheated on me. All men are terrible.
I read a study published by a pharmaceutical company that said that Accutane was safe. Maybe the government was too quick to pull this drug off the market.
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Chase is not very good-
looking, and he dresses badly. I don’t know how he can be a good architect. No fictional character has ever had a fan club. Harry Potter does, but he is the exception.
Two weeks ago, my instructor refused to accept a late paper. She did the same thing last week. Yesterday, she also told someone that because his paper was late, she wouldn’t accept it. I’d better get my paper in on time.
EXERCISE 5.8
Read the inductive paragraph below, written by student Pooja Vaidya, and answer the questions that follow it.
Years ago, when my friend took me to a game between the Philadelphia Eagles and the Dallas Cowboys in Philadelphia, I learned a little bit about American football and a lot about the behavior of football fans. Many of the Philadelphia fans were dressed in green and white football jerseys, each with a player’s name and number on the back. One fan had his face painted green and wore a green cape with a large white E on it. He ran up and down the aisles in his section and led cheers. When the team was ahead, everyone joined in. When the team fell behind, this fan literally fell on his knees, cried, and begged the people in the stands to support the Eagles. (After the game, several people asked him for his autograph.) A group of six fans sat without shirts. They wore green wigs, and each had one letter of the team’s name painted on his bare chest. Even though the temperature was below freezing, none of these fans ever put on his shirt. Before the game, many fans had been drinking at tailgate parties in the parking lot, and as the game progressed, they continued to drink beer in the stadium. By the beginning of the second half, fights were breaking out all over the stadium. Guards grabbed the people who were fighting and escorted them to a holding area under the stadium where a judge held “Eagles Court.” At one point, a fan wearing a Dallas jersey tried to sit down in the row behind me. Some of the Eagles fans were so threatening that the police had to escort the Dallas fan out of the stands for his own protection. When the game ended in an Eagles victory, the fans sang the team’s fight song as they left the stadium. I concluded that for many Eagles fans, a day at the stadium is an opportunity to engage in behavior that in any other context would be unacceptable and even abnormal.
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Which of the following statements could you not conclude from this paragraph?
All Eagles fans act in outrageous ways at games.
At football games, the fans in the stands can be as violent as the players on the field.
The atmosphere at the stadium causes otherwise normal people to act abnormally.
Spectator sports encourage fans to act in abnormal ways.
Some people get so caught up in the excitement of a game that they act in uncharacteristic ways.
Paraphrase the writer’s conclusion. What evidence is provided to support this conclusion?
What additional evidence could the writer have provided? Is this additional evidence necessary, or does the conclusion stand without it?
The writer makes an inductive leap to reach the paragraph’s conclusion. Do you think this leap is too great?
Does this paragraph make a strong inductive argument? Why or why not?
