Reasoning Skills and Determining Causes Help (page 3)
Introduction to Reasoning Skills and Determining Causes
"Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind."
—Leonardo da Vinci, Italian scientist, mathematician, inventor, sculptor, and writer (1452–1519)
This lesson will discuss the inductive reasoning approach to determining causes. It will also go over some of the common mistakes in reasoning people make when determining cause and effect.
The lesson Explanations for Arugments Help discussed how explanations are different from arguments. This lesson will look at a specific type of argument: the causal argument. The main difference between an explanation and a causal argument is simply in the way the argument is arranged. In an explanation, like in deductive reasoning, you look at the conclusion ("I was late") and then test the validity of the premises ("because my car broke down"). In a causal argument, on the other hand, the inductive approach is used: Evidence (what happened) is looked at, a conclusion is drawn about the cause based on that evidence, and then the validity of that conclusion is considered.
Just as there are criteria for testing explanations, there are also strategies for evaluating causes. Similarly, just as explanations can use false reasoning, there are also logical fallacies that can be committed in causal arguments. This chapter will start by addressing the two main strategies for determining cause and then discuss how to avoid the fallacies that often go with them.
When you are presented with an effect and want to inductively determine the cause, there are generally two techniques to use: looking for what's different and looking for what's the same.
Looking for the Difference
Your car wasn't running well on Wednesday. Normally, you use Ultra-Plus gasoline from the station down the street, but on Tuesday, you were low on gas and on cash, so you pulled into a station near your office and got half a tank of the cheapest brand. On Thursday, you went back to your regular station and filled up with your normal gas. By Friday, the car was running fine again. You did nothing else to your car, and nothing else was out of the ordinary.
So what caused the problem?
If you guessed the cheap gasoline, you're probably right. Though there are many things that can go wrong with a car and only a thorough inspection could tell for sure, the given evidence points to the cheap gas as the culprit. Why? Because the cheap gas is the key difference. Let's recap the facts: Your car ran well on your usual gas. When you changed the brand and grade, your car didn't run well. When you went back to your usual gas, your car ran fine again. The difference? The gasoline. Therefore, it's logical to conclude that the gasoline caused your car to run less smoothly.
Though in this example, it's obvious that the gasoline was the key difference, it isn't always so easy to determine causes. Read the following argument:
Every day for the past three months, you've been getting coffee from Lou's Deli, right around the corner from your office. One day, however, Lou's is closed, so you decide to try Moe's Deli across the street. You get your coffee and go to work. An hour later, you have a terrible stomachache. The next day, Lou's is open again and you get your usual coffee. You feel fine the rest of the day. "It must've been Moe's coffee that gave me that stomachache yesterday," you conclude.
This does seem like a logical conclusion, based on the evidence. After all, what's different between today and yesterday? It was Moe's coffee that was the difference, so Moe's coffee was the cause. Right?
Not necessarily. It is quite possible that Moe's coffee did indeed cause your stomachache. However, this conclusion can't be accepted without reservation—you can't say it's likely that Moe's coffee is to blame—until you ask a key question:
Were there any other relevant differences that may have caused the stomachache?
In other words, you need to consider whether there could have been something else that caused your stomachache. For example, maybe late the night before you ate spicy Chinese food. Or maybe you were really nervous about a big meeting that day. Or maybe you skipped breakfast and had an upset stomach to begin with. Any one of these possibilities could have been the cause.
The more possibilities there are, the less confident you should be that Moe's coffee is the culprit. However, if there isn't anything else unusual that you can think of, and especially if you get sick if you try Moe's again, then it's much more likely that Moe's is to blame. Either way, before you pinpoint your cause, be sure to consider whether or not there could be other relevant differences.
One way to sharpen your skill in finding the differences is to practice. Get a book of photographs that are of the same thing with subtle differences built in. See how quickly you can solve each one. It will help you pay closer attention to the details.
Looking for the Common Denominator
Sometimes, the cause can be determined not by looking for what's different, but by looking for what's the same—that is, something that each incident has in common. Take the following scenario, for example:
- Jason has been having trouble sleeping a few nights a week. On the nights when he can't sleep, he notices that the neighbor's dog is always barking and howling. Jason concludes that his trouble sleeping is due to the dog.
Jason has used a logical approach to determine the cause of his insomnia. He's looking for a pattern—something that is consistent with the nights he can't sleep. Because he hears the dog barking and howling on those nights, it could be that the dog is preventing him from getting his sleep. The dog is the common denominator for all of these occasions.
Just as it is important to be careful not to overlook other possible differences, however, it's important to remember to look for other possible common denominators. Before Jason concludes that his sleeplessness is because of the dog barking, he should carefully consider whether there might be anything else in common on those nights that he can't sleep.
So let's complicate the situation just a bit by adding more evidence from which to draw your conclusion.
Jason has been having trouble sleeping a few nights a week. On the nights when he can't sleep, he notices that the neighbor's dog is always barking. He also realizes that the sleepless nights are always nights that he hasn't talked to his girlfriend. Moreover, those are nights that he skipped going to the gym because he worked late. What's causing Jason to have trouble sleeping?
- the dog barking
- not talking to his girlfriend
- not exercising
- none of the above
Can you answer this question with confidence? Probably not. That's because each of these answers is a legitimate possibility. Each situation occurs on the nights Jason can't sleep. Just like the coffee may not have been the only thing different in the previous scenario, here, the dog isn't the only common denominator. There are many possibilities. If you're to confidently say which of these is the cause, you need to pinpoint just one event in common with all the bad nights.
If Jason knew that the dog barked every night—even on those nights when he is able to sleep—then the barking dog could be eliminated as an option. Similarly, if Jason skips the gym on other occasions when he can sleep, then choice c could be eliminated. But until more evidence is given and the other possibilities can be eliminated, none of the choices can be chosen over the others.
Post Hoc, Ergo Propter Hoc
Nina, who'd always dressed rather plainly, decided it was time to jazz up her wardrobe. She went shopping and bought a closet full of new, brightly colored clothing. Two weeks later, she was promoted at work. "Wow," she told her friend, "I had no idea that what I wore to work could make such a difference. Just changing my wardrobe finally got me that promotion I'd been waiting for!"
Nina deserves congratulations, but not for her reasoning. What's wrong with her logic here?
Nina has committed the post hoc, ergo propter hoc inductive reasoning fallacy. Post hoc, ergo propter hoc literally means after this, therefore because of this. Nina has assumed that because her promotion came after she changed her wardrobe, her promotion was caused by her change in wardrobe. Maybe, just maybe, her appearance did have something to do with it. But in all likelihood, there were several other causes for her promotion. She'd probably been doing good work for months or years, for one thing, and the position to which she had been promoted may not have been vacant before. There may be several other reasons as well.
Of course, cause and effect is a chronological structure—the cause must come before the effect—but remember that you need to consider other possible causes. Just because A comes before B doesn't mean there's a logical connection between the two events.
- Here's another example of post hoc:
After the Citizens First Bill was passed, crime in this area skyrocketed. Funny how the bill that was supposed to reduce crime actually increased it!
Notice how this argument assumes that because the Citizens First Bill came first and the rise in crime came second, one caused the other. But proving that there's a link between the two events would not be easy, especially since an increased crime rate could be caused by many different factors. In fact, a figure as complicated as crime rate is probably caused by a multitude of factors. What else can you think of that might have caused the increase in crime?
- Other possible causes:
You may have listed other possible causes like the following:
- An increase in unemployment
- A recession
- A change in population in the area
- A reduction in the police force
In fact, because human society is so complex, most social issues have multiple causes. In all likelihood, the increase in crime was caused by a combination of these, and possibly other, factors. But the Citizens First Bill, unless it specifically cut jobs and reduced the police force, is not to blame. It may have come first, but it's not necessarily the cause.
Cause and effect can be illustrated in many of the science experiments you have done in class. Think about being in the lab. What happened when you combined certain elements? They were the cause. What was the effect?
This seems like a reasonable argument, not a post hoc error. Part of the logic comes from the fact that bike riding works the calf muscles a great deal and could easily cause cramps.
The Chicken or the Egg?
- "I'll tell you why people today have short attention spans," your friend says to you one day. "It's because we are living in such a fast-paced society."
Maybe—but this is not necessarily true. Before you accept your friend's theory, consider that he could have just as easily argued the reverse:
- "We are living in a fast-paced society because people have such short attention spans today."
Which argument is the right one? Does living in a fastpaced society cause short attention spans, or do we live in a fast-paced society because people have short attention spans?
Again, both arguments try to simplify a topic that's very complicated. It's very hard to know what came first, a fast-paced society or short attention spans—the chicken or egg dilemma. You need to think carefully about the relationship between the two events before you come to any conclusions.
- Here's another example:
- Lucy feels more confident because she aced her last two exams.
True, getting good grades can boost your self-esteem. But it is also true that someone who feels confident is likely to perform better on an exam than someone who does not. So this is another case where cause and effect could go either way: Lucy's increased confidence could be caused by her good grades, but it's equally likely that her good grades were caused by her increased confidence. In such a case, it's best to suspend judgment about the cause until more information is known.
Reasoning Skills and Determining Causes In Short
There are two main approaches to determining causes in inductive reasoning: looking for what's different and looking for the common denominator. It is important to remember to look for other possible differences or common causes. Causal arguments should avoid the post hoc, ergo propter hoc fallacy, which assumes that because A came before B, A caused B. Finally, some causal arguments fall into the chicken or egg trap, where the argument that A caused B is just as strong as the argument that B caused A. Think carefully before accepting such an argument.
Skill Building until Next Time
- Be on the lookout this week for errors in causal reasoning. People are often quick to assign cause and neglect to think about other possible differences or common denominators. See if you can catch others—or even yourself—making these mistakes and correct them.
- Read some history. Historical texts explore cause and effect in detail, and they'll help you see just how complicated causes can sometimes be. This will help you realize how careful you need to be when evaluating cause and effect.
Exercises for this concept can be found at Reasoning Skills and Determining Causes Practice.
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