November 3, 2009

Homework #23 Answer

Children never develop strong self-esteem if they are guided by adults who criticize them. Therefore, if children are guided by adults who never criticize them, they will develop strong self-esteem.

Which one of the following arguments is most similar to the flawed pattern of reasoning used in the argument above?

This was a very difficult question. Parallel reasoning questions are probably the hardest, because you have to completely ignore the subject matter and substance of the stimulus and only consider its structure. Whether the argument in the answer choice is true, valid, believable or reasonable is entirely irrelevant. In this case, the question stem actually tells you that the argument in the stimulus is wrong because it depends on flawed reasoning, which means you already know it's not a reasonable argument. The question is not which of the following arguments seems reasonable, or likely to be correct. The question is which of the following arguments makes the same mistake of logic that the stimulus does, and is unreasonable for the same reason.

Completely ignoring the subject matter, and looking only at the structure of the argument, the stimulus is suggesting a cause-and-effect relationship where the occurrence of one event (X) causes the non-occurrence of another (Y). On other words, if X happens, Y will not happen. The flaw in the logic is the conclusion the author draws based on this relationship, i.e., the idea that if X does not happen, Y will happen, which is not logically sound. Just because X prevents Y from occurring, doesn't necessarily mean that the absence of X will cause Y to occur. Another example:

If you buy a sprinkler system, your house won't burn down. Therefore, if you don't buy a sprinkler system, your house will burn down.

This is flawed reasoning. The absence of a sprinkler system cannot by itself cause your house to burn down, nor does it guarantee by itself that your house will burn down. Of course, if your house catches fire, that's something else, but it's not part of the equation. The absence of a sprinkler system cannot cause it to catch fire, even though it might prevent you from putting that fire out. Just like in the stimulus; the absence of criticism from adults does not by itself guarantee that a child will develop high self-esteem, although it might contribute to that result.

The flawed logic can be formulated thusly: If X, then not Y; therefore, if not X, then Y.

A. Even though Hannah studies hard, she does not get good grades. Therefore, Hannah should not try to get good grades by studying hard.

(A) is incorrect because even though it is unreasonable, it is not so for the same reason as the stimulus. What's missing with respect to the stimulus is that the second sentence does not purport to guarantee that Hannah will get good grades if she does not study hard. (A) suggests not so much a cause-and-effect relationship but a method-and-goal relationship, specifically that the method has not thus far worked to achieve the goal, therefore Hannah should not continue to try this method. It's not entirely unreasonable; if a method doesn't work, try another method. In the context of this subject matter, though, it's bad advice.

B. Telephone salesmen who have bad phone manners do not sell any products. Therefore, telephone salesmen with low sales records must have bad phone manners.

(B) is also unreasonable but it's also incorrect. The flaw in the logic here is not that the non-occurrence of X guarantees the occurrence of Y. It's that X tends to cause Y, so if Y occurs, then X must be the cause. It's a simple cause-and-effect equation, simpler than the stimulus in that it merely inverts the cause and effect. Even though Y is a negative event (" not sell any products"), it's in the negative on both sides of the equation. The stimulus' pattern reverses the negations between X and Y (If X, then NOT Y; therefore if NOT X, then Y). This choice does not (If X, then NOT Y; therefore if NOT Y, then X).

C. Using the store's new knitting machine, the knitting store owner made twice as many sweaters yesterday as she did the day before. Therefore, if she uses the knitting machine again tomorrow, she will make twice as many sweaters as she did today.

(C) is incorrect because it also does not match the pattern of the stimulus' argument. For one thing, there are no negative events here. The statement is flawed because it assumes that because one event caused a changed outcome, a repetition of that event must cause the change (not the event itself) to occur again. The statement is absurd because the change in the outcome was attributable to a changed condition. If the new condition subsequently remains the same and does not change again, then the change in the outcome will not recur.

D. Puppies who are not used to being with people do not interact comfortably with a large group of people. Therefore, the more a puppy is used to being with people, the more comfortable he will be with a large group of people.

(D) is incorrect because it's not flawed; it's a perfectly reasonable statement.

E. People who take calcium supplements do not increase their risk of heart disease. Therefore, people who do not take calcium supplements will increase their risk of heart disease.

(E) is correct because it's the only choice that matches the pattern of the stimulus (If X, then not Y; therefore, if not X, then Y). In this case, X is the taking of calcium supplements, and Y is an increased risk of heart disease.