Analyzing Flaw Stimuli from a Structural Perspective

Download a preview of

LR Perfection Free Preview: Chapter 8 Part I

Flaw Questions are the most common questions to appear on the Logic Reasoning section, making up over 20% of all questions in total. It is also the only question type that can only be solved via outside knowledge. For nearly every other type of question, we can learn them by practicing and examining the questions, but for Flaw Questions, there are material that we must learn and memorize.  

Flaw Questions are also noted for their hard to decipher answer choices, so we will continue to practice the art of matching keywords from answer choices with information in the stimulus. (Just as we did with Role and Method Questions.)

Flaw Questions will contain a problematic argument in the stimulus (remember we mentioned before that for the majority of LR questions, the stimulus will contain an argument). Flaw Question stimuli will ALWAYS contain an argument, which means that it will have a main conclusion, premises, and maybe an intermediate conclusion.

As usual, the first step when approaching Flaw Questions is to dissect the stimulus and identify components of the argument, just as we did in Find the Conclusion, Role, and Method Questions. 

Once we have identified the support and the conclusion in the author’s argument, we need to find what’s wrong with the argument. Take a look at the following argument:

All men are mortal.

Socrates is a man.

Therefore, Socrates is mortal.

This is Aristotle’s most famous syllogism. You have probably seen it before. It is a valid argument, we can find no fault with it, and as a result, it is without flaw.

An argument may be logically valid but still false, as seen in the example below:

All men are unicorns.

Socrates is a man.

Therefore, Socrates is a unicorn.

This is still a valid argument, despite all its ridiculousness. In real life, you could refute this argument by pointing out the falsehood of its premise: the statement all men are unicorns is false. So even though the argument is still valid, it’s not a sound argument.

But on the LSAT, we are not here to dispute the truthfulness/falsity of the argument’s premises. In other words, we do not care whether the statements in the argument are true in real life. All we care about is the validity of the argument.

But how do we determine whether an argument is valid or not? Take a look at the following example:

All men are mortal.

Socrates is probably a man.

Therefore, Socrates is mortal.

This argument is imperfect. In fact, it is invalid. We accept each premise as true, but the author’s premises do not warrant the conclusion. If Socrates is probably a man, then the only conclusion you can derive is that Socrates is probably mortal. There is a shift in the language of the argument going from premise to conclusion. The author makes a certain conclusion based on what is probable.

In fact, in every flaw argument, there will be an unsupported leap made going from the premises to the main conclusion. Sometimes it’s between one of the premises and the main conclusion, sometimes it’s between the intermediate conclusion and the main conclusion. But it will always involve the main conclusion and another supporting statement.

Because the author has made a “leap of reasoning,” there will be gaps in the author’s reasoning, as a result.

 Our second step is therefore to think about the gap in the author’s reasoning and ask ourselves whether this leap is reasonable. 

Take a look at the following example: 

David is going to law school, therefore he must have taken the LSAT. 

What is the premise in this argument? 

David is going to law school,

What is the conclusion in this argument?

David has taken the LSAT.

Are there any gaps in the author’s reasoning? Well, we know that not everyone who is going to law school will have taken the LSAT. Maybe they took the GRE instead. Perhaps the law school David is attending doesn’t require the LSAT. Perhaps David is attending an LLM or JSD program.

In other words, the premise in the example above does not automatically lead to the conclusion. When analyzing the Flaw Question stimulus, our job is to find that gap in the author’s reasoning. Sometimes the gap is pretty obvious, as we saw in the first example. But other times, we must think about whether the premise/intermediate conclusion will automatically lead to the main conclusion, or has something less obvious been overlooked.

8.1.1 Shifts from Premises/Intermediate Conclusion to the Main Conclusion

A technique that really helped me find the gap in the author’s reasoning is to compare the wording of the supporting premises and the conclusion, looking for shifts in scope, quantity, intensity, logic, and concepts. Let’s look at a question stimulus. 

The probability of avoiding heart disease is increased if one avoids fat in one’s diet. Furthermore, one is less likely to eat fat if one avoids eating dairy foods. Thus the probability of maintaining good health is increased by avoiding dairy foods. 

The stimulus of this question is not hard to understand. There is no peripheral information in this stimulus; it contains two premises and a conclusion. Let’s rearrange it in logical order: 

Premise: One is less likely to eat fat if one avoids eating dairy foods

Premise: The probability of avoiding heart disease is increased if one avoids fat in one’s diet

The premises, when linked, give us this: Avoid dairy Less likely to eat fat More chance of a healthy heart/higher chance of avoiding heart disease   

Now let’s look at the conclusion of the argument: 

Conclusion: Thus the probability of maintaining good health is increased by avoiding dairy foods

In other words, Avoid dairy More chance of maintaining good health

Notice the term shift? The scope of the conclusion widened considerably compared to that of the premises. The premises tell us that avoiding dairy can help us avoid heart disease, but the conclusion is now about health in general. 

***

So remember to look at the supporting premises and the conclusions of Flaw Questions separately. Compare and contrast the differences between the two, and ask yourself if the author has made any leaps of reasoning or left gaps in the argument when deriving the conclusion from the premises. 

Let’s look at another question where we have to consider the differences between what the author is talking about in the premises and what they are talking about in the conclusion. 

PT40 S3 Q19

Fishing columnist: When an independent research firm compared the five best-selling baits, it found that Benton baits work best for catching trout. It asked a dozen top anglers to try out the five bestselling baits as they fished for speckled trout in a pristine northern stream, and every angler had the most success with a Benton bait. These results show that Benton is the best bait for anyone who is fishing for trout.

Each of the following describes a flaw in the reasoning in the fishing columnist’s argument EXCEPT

A. The argument overlooks the possibility that some other bait is more successful than any of the five best selling baits

B. The argument overlooks the possibility that what works best for expert anglers will not work best for ordinary anglers

C. The argument overlooks the possibility that the relative effectiveness of different baits changes when used in different locations

D. The argument overlooks the possibility that two best selling brands of bait may be equally effective

E. The argument overlooks the possibility that baits that work well with a particular variety of fish may not work well with other varieties of that fish 

What is the author’s conclusion in this question?

Benton is the best bait for anyone who is fishing for trout. 

So the author concludes that Benton is the best, not one of the best, not the second best, but number one, and for everyone who is fishing for trout. That’s a pretty big claim. How does the author support their conclusion? Let’s go through the author’s supporting premises one by one, looking for gaps between the premise and the conclusion. 

When an independent research firm compared the five best selling baits, it found that Benton baits work best for catching trout. 

Ok, so the study was done by an independent research firm, that’s good, perhaps there is no conflict of interest here. But why did they only compare the five best selling baits? We know already that the conclusion is that Benton is the best for anyone looking to catch trout, not just the best among best selling baits. There is a significant gap here. Is it possible that the best bait is not the best-selling bait? Yes. The best-selling cars are probably Corollas, Camrys, Civics, etc. But are these the best cars? It’s possible that some products sell well due to their price point or availability in stores. 

It asked a dozen top anglers to try out the five bestselling baits as they fished for speckled trout in a pristine northern stream

There are three potential issues here: the people testing the bait were all top fishermen. If Tiger Woods thinks a golf club is the best, does it mean it’s the best for anyone looking to golf? Not necessarily: something that works for the pros might not work for beginners. Secondly, they were fishing for a very specific type of trout. If something works for speckled trout, would it work equally well for other types of trout, like rainbow trout? Thirdly, the fishermen were fishing in a pristine northern stream. Would it work equally well in a lake or elsewhere?

When we line up the premises and compare it to the conclusion, we find significant gaps in the reasoning. The differences in scope between the two are glaring. This is what we know:

Premises

  • Pros liked Benton bait
    • Gap: just because pros think its good doesn’t mean it’s suitable for everyone
  • Only five top selling brands were tested
    • Gap: could there be really good brands that don’t sell well that the study missed out on?
  • The testing was done in a pristine northern stream
    • Gap: what about trout living in lakes? Or in the south?
  • They were fishing for a very specific species of trout
    • Gap: would the bait work for other species of trout

Conclusion:

  • Benton is the best for anyone looking to fish for trout

So once we have isolated and compared the premises and the conclusions, we try to think of potential objections to the author’s reasoning. Is the author’s reasoning valid? Can we brainstorm potential ways to rebut the author’s argument?

Let’s take a look at the answer choices:

One thing to note here is that this is an EXCEPT question. This means that the way we approach the answer choices is essentially reversed: instead of looking for the flaw in the question, we are eliminating the four answer choices that correctly state flaws that appeared in the argument. The correct answer is in fact irrelevant to the argument. 

A. The argument overlooks the possibility that some other bait is more successful than any of the five bestselling baits.

If something is overlooked, then that information can potentially hurt the argument. We will look at “overlook” answer choices in further detail later in the chapter. 

Is this piece of information something that can potentially hurt the argument? Yes: the best bait is not necessarily the best selling. This is one of the gaps in reasoning we have discovered previously. 

B. The argument overlooks the possibility that what works best for expert anglers will not work best for ordinary anglers

This answer choice also matches up with one of the gaps in reasoning we have identified. 

C. The argument overlooks the possibility that the relative effectiveness of different baits changes when used in different locations. 

We have also identified this as a gap in the author’s reasoning. The testing was done in a pristine northern stream. Would it also work as well in a lake in the south? 

D. The argument overlooks the possibility that two best selling brands of bait may be equally effective

This is NOT one of the gaps we have identified. Is it possible that there is another brand of best-selling bait that is just as good as Benton’s? No: the stimulus clearly states that Bentons is the best among the five best selling baits. 

E. The argument overlooks the possibility that baits that work well with a particular variety of fish may not work well with other varieties of that fish

Something that works with speckled trout may not work with rainbow trout. This is also a gap that we have identified. 

The correct answer is D. 

Step 3 of analyzing a Flaw question stimulus is therefore to think of potential objections we can make to the author’s reasoning once we have identified the gap between the premise and conclusion. 

8.1.2 Most Commonly Seen Flaw Patterns (Fallacies)

However, simply noticing the gap between the premise and the main conclusion is not enough to guarantee success on Flaw Questions. Many of the invalid arguments in Flaw Questions correspond with famous reasoning fallacies such as the slippery slope, the strawman, or ad hominem. (By my count, about 40-50% of all Flaw arguments correspond with one of the following fallacies.) Here is a list of 21 fallacies that have commonly appeared in Flaw Questions.

Commit each of these to memory, google them for examples if need be, and try to match up the gap in the stimulus argument with these if you can.

1. Sampling bias

Sampling errors occur when the author extrapolates the qualities of a sample unto the whole population. Whenever we see the argument stimulus talking about a survey, sample, or study, we ask ourselves whether sampling bias is involved. 

Having a survey/sample present in an argument doesn’t automatically mean bias is present (as we can see from the question earlier in the chapter). In fact, sampling bias is one of the most frequent red herrings to appear in Flaw questions. More specifically, the author will talk about a survey in the argument, thereby tricking the test taker into thinking it’s a sampling flaw we are dealing with. But in reality, the survey itself has no problems, and the flaw is hidden deeper in the argument. 

So whenever we see that a sample/survey is present, ask ourselves the following questions: is the sample size representative of the population? Are there flaws or biases in the survey methodology? If not, then the flaw will lay elsewhere. 

Questions to consider: 59-2-20, 74-4-18

2. Ad hominem 

Ad hominem, or personal attacks are less frequent in harder Flaw Questions. But look out for arguments where the author is refuting another point of view by criticizing the source rather than the opponent’s argument. Perhaps the opponent doesn’t practice what he preaches, or they can have questionable motives. Be careful when the opponent’s argument is not directly addressed. 

Questions to consider: 77-2-18

3. Appeal to authority 

Appealing to authority is problematic in two scenarios: 

First, when the only support provided for a point of view is that the person voicing the claim or supporting the claim is an expert. For example, if we argue that “we should believe John simply because he is an expert, ” the author commits the appeal to authority fallacy. Experts, just like everyone else, need to back up their claims with credible evidence. 

Second, whenever an expert’s voice is thrown into the mix, we have to ask ourselves whether the expert is the appropriate authority in this case. Are they qualified to speak on the matter? Does what we are discussing fall into the scope of their expertise?

Questions to consider: 21-2-25

4. Appeal to ignorance

Appeal to ignorance, or “unproven vs. untrue,” as many like to call it, is where we accept a view due to the lack of evidence to the contrary. The argument “aliens exist because there is no evidence to prove that they don’t”, or “there is no God because you can’t prove his existence” are both appeals to ignorance. 

In other words, you can’t prove/disprove a thesis or conclusion simply because there is no way to prove the contrary. 

Appeal to ignorance fallacies are quite common in Flaw Questions. But in the majority of cases, the test makers will present a variation of this fallacy. Instead of suggesting that the opponent’s view is false because there is no evidence to prove it true, the author will argue that the opponent’s view is false because the opponent’s argument is weak. The author may point out the opponent’s reasoning has gaps in it, and then hastily rejects the opponent’s conclusion. 

I call this the “Weakness – Reject” variation. The author in the stimulus finds certain weaknesses in the opponent’s reasoning and jumps to the conclusion that the opponent’s view is thereby wrong and rejects it. It’s a more commonly seen variation of the Appeal to Ignorance/Unproven vs. Untrue fallacy. 

Let’s take a look at the following example: 

John: Socrates died in his old age, therefore all men are mortal. 

David: You cannot extrapolate from one person to all men, therefore there must be some men who are immortal. 

Here, David points out a legitimate issue with John’s argument (weakness), and goes on to deny wholesale John’s conclusion (reject). Pointing out a weakness in the opponent’s reasoning doesn’t automatically negate their conclusion, it only weakens it. 

Questions to consider: 20-4-18, 20-4-22, 26-2-21, 29-1-17, 45-4-24, 64-3-14, 72-3-11

5. False dichotomy 

False dichotomy or false choice fallacies do not appear frequently. It occurs when two options are presented, the author rejects one, and concludes that the alternative option is the only possibility left. If the stimulus clearly states that only two choices are available, then rejecting one and being left with only one choice is not flawed reasoning. However, sometimes we do not know if the two choices presented are the only options available. In this case just because one option is unavailable, it doesn’t mean we have to choose the alternative. Take a look at the following example: 

The only ways to go to Hawaii are by plane or boat, no boats will sail due to the hurricane, so we have to fly. (This reasoning is valid because we know that only two choices are available.)

You can go to Canada by flying or driving. Flights have all been grounded due to Covid, so we have to drive up there. (This argument suffers from the false dichotomy fallacy. Flying and driving are possibilities, but we don’t know if they are the only possibilities. So potentially, you can go by train as well.)

Be sure to distinguish the false dichotomy fallacy from the selective attention fallacy, which we will look at down the road. 

Questions to consider: 44-4-22

6. Fallacy of Composition/Division

The fallacy of composition/division is an informal logical fallacy commonly called “part vs. whole” on the LSAT. This fallacy occurs when there is an entity that can be divided into multiple parts in the stimulus. The author erroneously extrapolates the entity’s properties unto its composites (believing what is true of the whole must be true of its parts). Alternatively, the author takes a property of the composite and believes it is also applicable to the entire entity (believing what is true of the parts must be true of the whole). 

For instance, the erroneous argument “The US military is the most lethal fighting machine in the world, so each of its individual soldiers must also be the best fighters in the world as well” makes the mistake of extrapolating a property of the whole to an individual part of that entity. 

It is important to note that extrapolating a property of the whole to the part or vice versa is NOT automatically fallacious. We have to examine the reasoning on a case-by-case basis.

For instance, if I said, “Every part of this ship is made out of steel, therefore this ship is made of steel,” then there is nothing wrong with the statement. However, if we try to extend a property that should not be extended from parts to the whole or vice versa, then it becomes problematic. If my argument was instead, “Steel components sink in water, so this ship, made entirely of steel, will no doubt sink as well, ” I would have committed the part vs. whole fallacy. 

It is important to note that the fallacy of composition is not the same as sampling bias. These two fallacies are similar in the sense that you are extrapolating a property from a part to a whole. But with the sampling bias, you are estimating some characteristic of a population based on a subset or sample. In contrast, with the fallacy of composition, there is no requirement for the whole entity to consist of a population. 

Questions to consider: 23-3-16, 44-4-11, 77-2-22, 

7. Equivocation

Equivocation occurs when a specific word with multiple meanings is used in the author’s argument, but the word’s meaning subtly shifts as the argument moves from premise to conclusion. Look at the following example: “Bringing a gun into the classroom is a criminal offense, so we should arrest all the gunners in my law school class.” 

Equivocation flaws frequently appear in harder Flaw Questions, and it’s important to read the stimulus carefully and closely examine recurring words. 

In the hardest equivocation flaw questions, the second equivocate usage of the word will not appear explicitly in the stimulus. Instead, they form a part of the author’s assumptions. Because assumptions are unstated, we will not find the word by simply parsing the stimulus’ text. 

John: my opponent argues that political candidates must do whatever they can to enhance their credit. But unsustainable spending surely carries over from one’s personal life into one’s political agenda. I rather prefer the fiscally responsible candidate. 

In the example above, the word “credit” means “trust” in the first sentence, but in John’s subsequent argument, he interprets “credit” to mean financial obligations. Even though the word “credit” only appears once in the example, the argument’s flaw is based on a misinterpretation of the word “credit.” 

Questions to consider: 1-3-22, 22-2-12, 22-2-24, 22-4-18, 26-2-15, 59-2-15

8. Percentage vs. Amount

Confusing a percentage change with a change in net amount is also a common flaw. For example, the author mistakenly assumes that a greater percentage increase means a greater net increase. 

When the concept of percentages appears on any Flaw Question, I will immediately check for such an error. Three figures are at play in percentage vs. amount questions: total sum, percentage change, and change in amount. We need two to derive a conclusion about the third figure. Take a look at the following example: 

Rwanda’s GDP increased at 15% last year, while the US only increased 5%. So Rwanda’s economic expansion was bigger than the US’s last year. 

Percentage is based on the pre-existing size of the pie: the American economy is much larger than the Rwandan economy. 

Any question that only gives us one out of the three figures (total sum, percentage change, change in amount) and makes a conclusion about another figure will have committed the percentage vs. amount flaw. We need to provide the other two to come to a proper conclusion about any of these figures. 

Questions to consider: 6-3-24, 48-4-25, and an especially tricky/well-disguised one: 71-3-22

9. Circular Reasoning 

Circular reasoning is essentially the conclusion repeating the information stated/assumed in the premise. In its most basic form, it looks like this:

Premise: A

Conclusion: A

Because of A, therefore A. 

Of course, circular reasoning flaw conclusions on the LSAT will not simply repeat what was stated in the premise verbatim. The language will be slightly different but still express essentially the same idea. Take a look at the following two examples: 

New York is the best city in the world because no city is better. 

Premise: no city is better than New York (New York is the best)

Conclusion: New York is the best city in the world

Surely the egg came before the chicken, otherwise where would the first chicken have come from?

Premise: if the egg didn’t come before the chicken, then we can’t adequately explain chickens’ origins. (Assumption: the egg came before the chicken)

Conclusion: the egg came before the chicken. 

In the second example, the author’s conclusion is not a simple restatement of the supporting premise, but rather, the point made in the conclusion is assumed in the premise’s reasoning.

This is more common in the harder circular reasoning type questions. So always beware of arguments that contain no new information going from the premise to the conclusion, and keep an eye out for unstated assumptions. 

 

Questions to consider: 49-2-23, 82-1-22 

 

10. Self Contradiction

Self-contradiction flaws occur when the conclusion contradicts some of the information already presented in the rest of the stimulus/argument. This is quite easy to spot in easier questions. However, the contradiction will be harder to spot in the hardest questions. The author will often mask the contradiction behind complicated language and assumptions or require the test taker to make the inference themselves. Take a look at the following examples: 

Although high cholesterol levels have been associated with the development of heart disease, many people with high cholesterol never develop heart disease, while many without high cholesterol do. Recently, above average concentrations of lipoprotein were found in the blood of many people whose heart disease was not attributable to other causes. Dietary changes that affect cholesterol levels have no effect on lipoprotein levels. Hence, there is no reason for anyone to make dietary changes for the sake of preventing heart disease. 

In the example above, the author concludes that because lipoprotein is unaffected by dietary changes, there is no reason to make dietary changes if your goal is to prevent heart disease. (The author is assuming that lipoprotein levels are the only factor in play here). However, the author also states that high cholesterol levels can cause heart disease (above-average concentrations of lipoprotein were found in the blood of many people whose heart disease was not attributable to other causes). Herein lies the contradiction: the author states that high cholesterol levels sometimes cause heart disease, then goes on to a conclusion that assumes only lipoprotein causes heart disease. 

To hold criminals responsible for their crimes involves a failure to recognize that criminal actions, like all actions, are ultimately products of the environment that forged the agent’s character. It is not criminals but people in the law abiding majority who by their actions do most to create and maintain this environment. Therefore, it is law abiding people whose actions, and nothing else, make them alone truly responsible for the crime. 

Can you find the self-contradiction in this example? The author concludes that it is law abiding people who are responsible for the crime. Why aren’t criminals responsible? Because their actions are products of the environment? But what about the actions of law-abiding citizens? The author states that all actions are ultimately products of the environment. According to the author’s reasoning, no one would be responsible, right? How can you argue that because criminals’ actions are products of the environment, so they are not responsible; but normal people are responsible even though their actions are also products of the environment?

These two examples represent the most challenging Self Contradiction flaws in general. The argument’s author can either present but then ignore a piece of contrary evidence, or present a piece of information that can lead us to an inference that contradicts the author’s conclusion. 

Questions to consider: 9-2-22, 12-1-24, 20-1-22, 33-3-17, 43-3-20, 47-3-19, 67-2-13, 83-1-22, 84-3-22

11. Inducing future from past events

This fallacy is quite easy to understand: the author assumes what was true in the past will continue to hold true in the future. Sometimes the author will dress this flaw up in conditional-like language to confuse you. Take a look at the following example: 

All presidents in the past have only been white males. So Barack Obama, who is black, cannot become president. 

Some students, seeing the words “all” and “only,” mistakenly believe the argument to be conditional. But remember, as we have discussed in Chapter 7, true conditionals should have universal applicability. Limited statements like these aren’t true conditionals, so you can’t contrapositive them and come to a valid conclusion. 

Questions to consider: 54-2-19, 74-4-20

12. Gambler’s Fallacy

The gambler’s fallacy occurs when we mistakenly believe occurrences in the past will influence the likelihood of random events occurring in the future. When you have a series of random events occurring in sequence, such as flipping a fair coin, or betting on black or red on the roulette table, each flip or roll is an independent event in itself. Just because you flipped five tails in a row, the probability of getting heads on the next coin toss is still 50/50. 

Gambler’s Fallacy vs. Law of Large Numbers:

Here is where some students get confused. The law of large numbers states that over an extended period of time or a large number of trials/coin tosses, we can expect a gradual regression to the mean. In other words, continuing with our coin toss example, assuming the coin is fair and we get 10 heads in a roll, 

Law of Large Numbers: 

First 10 tosses: 10 Heads (Heads 10 : Tails 0)

Next 100 tosses: 50 Heads/50 Tails (So 60 Heads/50 Tails after 110 tosses) (Heads 6: Tails 5)

Next 1000 tosses: 500 Heads/500 Tails (560 Heads/550 Tails after 1110 tosses) (Heads 56: Tails 55)

So on and so forth…

So the probability of each individual coin toss is not affected by previous results, but rather, the effect is lessened when you toss more and more, with the overall result getting closer to 1:1. 

A Special Note: There are instances when past occurrences WILL affect the probability of events occurring in the future. In such cases, the Gambler’s Fallacy is not applicable. For instance, if we are attempting to draw the Queen of Spades from a deck of 52 cards. Initially, the probability is 1/52. But after drawing 10 cards and still not getting the Queen of Spades, the likelihood that we get this card on the next draw has increased. It is now 1/42. For the curious student intent on doing additional research into the topic of conditional probability, start by looking into the general multiplication rule formula, or P(A ∩ B) = P(A) P(B|A).

13. Non sequitur fallacy (Unnecessary Extrapolation of Belief)

A non sequitur fallacy is where the conclusion does not follow the premise. On the LSAT, this flaw is manifested by extending an implication or result of a view unto the view holder:

I love junk food, junk food destroys the body, therefore I love to destroy my body. 

I believe studying hard will get me into law school, but going to law school will put me into a lot of debt, so I believe studying hard will put me into a lot of debt. 

Priests from the Middle Ages believed the plague to be a punishment from God. We now know that the plague was caused by bacterial infection. So medieval priests saw bacteria as a tool of God.

In reality, the argument’s conclusion in both examples above do not follow from the premise. I can either be unaware of the additional result of my view, disagree with it, or hold my view despite that result. The scope shifts/widens going from the premise to the conclusion, and that’s why we must keep in mind to compare the exact wording of the supporting premises and the main conclusion on Flaw Questions. 

14. Confusing conditional with causation

Essentially, the author argues that because B is necessary to A, B is the cause for A. So in other words, confusing A → B with B ⇒ A or A ⇒ B. 

As we have mentioned previously, harder LR questions can contain conditional and causal reasoning elements. But they must be considered independently, so don’t mix up the two. 

Alternatively, the author can present us with a causal relationship A ⇒ B, and derive a conditional relationship from it. This would be wrong as well. 

15. Appeal to probability/possibility 

This fallacy assumes that just because something could be true or is probably true, then it must be true.

Questions to consider: 29-4-18, 32-1-6, 35-1-17, 88-4-21

16. Selective Attention fallacy 

The selective attention fallacy, or cherry-picking, occurs when we are presented with two or more alternatives, and the author arbitrarily chooses one of them. The author selects one or the other without additional elaboration. So we are left wondering why the author chose A over B. In other words, the author overlooks the other possibility and selects one over the other in a seemingly random manner.  

Questions to consider: 83-3-15, 87-3-26

17. Relative/Absolute confusion 

The relative/absolute confusion is specific to the LSAT, and not considered an official informal fallacy in the philosophical sense. In the relative/absolute flaw, the author confuses a relative value with an absolute value. For example, the author will claim that because being slightly overweight is healthier than being severely underweight, being slightly overweight is a healthy condition. 

Another way the relative/absolute flaw appears is with the words “more” and “most.” This ties in directly with the equivocation and percentage vs. amount flaws. This kind of reasoning has appeared several times in Flaw and other types of questions: the author can argue that because Candidate X has the most votes out of all the candidates, more people voted for him than those who didn’t. The validity of this argument depends on the total number of candidates. If there are more than two candidates in the running, being the first past the polls doesn’t necessarily mean that you received more than 50% of the votes. 

Questions to consider: 53-1-22, 54-4-16, 65-4-26, 51-1-18

18. False Conversion

(We will look at this in greater detail in the chapter on Must be True Questions)

False conversion fallacies have to do with reversing the order of relationships in “all” and “most” relationships. We will look at some/most/all relationships in greater detail in the Must be True chapter, but for now, remember that “all” and “most” relationships cannot be reversed without committing a logical fallacy. 

All law students are college grads

All college grads are law students (false conversion) 

Most Americans are English speakers

Most English speakers are Americans (false conversion)

“Some” relationships can be reversed, 

Some Japanese people are English speakers

Some English speakers are Japanese (valid)

The only correct way in which we can reverse “most” and “all” relationships is by turning them into “some”:

All law students are college grads

Some college grads are law students (valid) 

Most Americans are English speakers

Some English speakers are Americans (valid) 

In some of the harder false conversion questions, the stimulus will not use terms such as “most” or “some”, these would be too obvious. Instead, percentages or likelihood will be substituted. Take the following example: 

70% of all smokers have lung disease, John has lung disease, so he is most likely a smoker. 

The argument in the example above is essentially a variation of the false conversion of “most”. In other words, most smokers have lung disease, so most people with lung disease are smokers (this is the flawed assumption of the argument and where the false conversion happens), John has lung disease and therefore his probability of being a smoker is high. 

Questions to consider: 4-1-23, 13-2-24, 27-1-23, 41-3-20

19. Appeal to extremes/slippery slope

This fallacy has rarely appeared in more recent tests, I would keep an eye out for it. The author appeals to extreme cases or improbable cases to justify their conclusion. 

Question to consider: 86-1-21, 57-3-8

20. Appeal to belief 

In the appeal to belief fallacy, the author argues that because people believe X, X is true. This is similar to the informal fallacy of argumentum ad populum, or appeal to popularity, which states that because most people/segments of the population believe X, X is true. In other words, the author confuses the opinion/beliefs of certain people with factual information. 

Questions to consider: 15-2-17, 32-4-13

21. Comparable Flaw (False Analogy) 

We have examined comparable reasoning/analogies in greater detail at the end of the previous chapter. The author will compare two concepts and argue that since A and B are similar in one aspect, they will be similar in another. Conversely, the author will argue that since A and B are dissimilar in one aspect, they must be dissimilar in another. 

The hardest comparable flaw questions will often contain traces of other types of reasoning in them as well, the most frequent being causal reasoning, we have already covered hidden and hybrid logical patterns in Chapter 7. Suppose the argument read, “Air pollution is the leading cause of lung disease in China, so to decrease incidents of lung disease here in the US, we must make every effort to clean up the air.” This is a hybrid argument (we discussed hybrid arguments in the previous chapter). It contains causal reasoning (air pollution as a cause of lung disease), but don’t forget that the argument, at its core, assumes a similarity between China and the US. 

Look at 23-2-21, 33-3-15, 46-2-11, 49-2-18, 52-3-16, 81-2-20, and 86-4-24 for a deeper understanding of how comparable reasoning/analogies are used in Flaw questions.

***

Here is a quick summary of what we have covered so far:

Find the Conclusion.

How is the Conclusion supported? (Isolate the premises provided for the conclusion)

Think about how the author goes from the premises to the conclusion: are there any gaps in the author’s reasoning, does the author make any unwarranted leaps going from premise to conclusion?

If we accept the author’s premises, can we make potential objections to the author’s conclusion?

Are there any term shifts between the wording in the premises and the conclusion? Have the scope, intensity, logic, and concepts discussed subtly changed?

Does the reasoning pattern match up with one of our classical fallacies?