Analyzing Arguments: The Basics of Logical Reasoning - Logical Reasoning: Picking Apart an Argument - LSAT For Dummies 

LSAT For Dummies, 2nd Edition (2014)

Part III. Logical Reasoning: Picking Apart an Argument

tip.eps Five Common Informal Fallacies Tested on the LSAT

Occasionally, the LSAT asks you to find the flaw in a formal argument. Some of the informal fallacies most commonly tested on the LSAT are these:

·        Fallacies of relevance occur when the conclusion isn't relevant to the premises offered to support it. Common forms are a red herring argument and an ad hominem attack.

·        Fallacies of weak induction occur when the premises don't adequately support the conclusion, such as fallacious appeals to authority and hasty generalizations.

·        Fallacies of ambiguity use unclear or undefined meanings.

·        Fallacies of presumption occur when someone's claim presumes an unsubstantiated truth. The argument may use circular reasoning or a false dichotomy.

·        Fallacies of analogy result from comparing entities that aren't sufficiently similar to warrant a comparison or from claiming that because the parts of a whole are a certain way, the whole is also that way, or because a whole is a certain way, the parts individually are also that way.

webextras.eps Ever wondered what the difference is between some and most? Get the lowdown on LSAT logical reasoning vocabulary at www.dummies.com/extras/lsat.

In this part…

·        Get the scoop on the components of logical arguments to better analyze LSAT logical reasoning questions.

·        Determine what sort of answer best weakens or strengthens a conclusion.

·        Find the flaw in a logical argument with one hand tied behind your back.

·        Discover the approach to a variety of logical reasoning question types.

·        Spot elements in logical reasoning answer choices that immediately signal an incorrect response.

Chapter 7. Analyzing Arguments: The Basics of Logical Reasoning

In This Chapter

arrow Knowing what to expect in the LSAT logical reasoning section

arrow Planning your approach to logical reasoning questions

arrow Understanding premises, conclusions, and types of reasoning

The LSAT logical reasoning questions test your ability to deconstruct statements. This section, like the rest of the LSAT, measures your ability to read carefully and quickly. Unlike the other sections (analytical reasoning and reading comprehension), the logical reasoning section doesn't immerse you in one text or one problem for several minutes. Logical reasoning rewards speed and flexibility. It primarily tests your informal logic ability, which is a lot like the kind of reasoning you use to determine whether you should purchase a $200 facial cream because an advertisement claims that applying it will make you look ten years younger.

remember.eps To add to the fun, every LSAT has two logical reasoning sections. The LSAT-makers think logical reasoning questions prove to be valuable in predicting law-school success, so on test day you spend at least 70 minutes answering these lovely little questions. Preparing for this section should be a priority; it makes up half your score, which is a big deal.

The good news is that you analyze arguments all the time, even though you may not know that's what you're doing. When you see a commercial advertising a new product that claims it'll make your life better, you probably question that claim. If a weight-loss drug helped someone lose 50 pounds, you may ask, “Is that a typical result?” If four out of five dentists recommend a chewing gum, you may say, “Did they ask only five dentists?” When a mutual fund boasts of its performance, you may ask, “Is that better than the market average?” This is the same kind of thinking that you use to ace the logical reasoning section on the LSAT.

In this chapter, you learn the basics of logical reasoning — how the sections are set up, the type of logic you apply to the argument, and the general approach to the section. Check out Chapters 8 through 10 for details about specific logical reasoning question types.

What You Can Expect in the Logical Reasoning Sections

A section of logical reasoning contains about 25 or 26 questions that you must answer in 35 minutes. Every question consists of a short statement called an argument — usually three to five sentences — followed by a question about that argument. You encounter short passages from a variety of sources, such as speeches, advertisements, newspapers, and scholarly articles.

For example, you may see an argument like this: “The local sales tax must be raised to fund city services. Admittedly, this increased sales tax will impose a greater hardship on the poorest citizens. But if the sales tax is not increased, all city services for the poor will have to be cut.”

The paragraph reflects the type of arguments that you encounter in the news every day. The questions may ask you to strengthen or weaken an argument, identify the argument's conclusion, or duplicate the argument's pattern of reasoning.

remember.eps The question contains all the information you need to answer the question. Don't rely on any outside information! Even if you happen to be an expert in the area a question covers, don't rely on your expertise to answer the question.

Each question has five possible answer choices, which are often long — sometimes even longer than the argument or question. For this reason, you spend most of your time for each question examining the answer choices.

tip.eps As with most LSAT questions, often you can quickly eliminate one or two of the answers because they're obviously wrong. The remaining answers are more difficult to eliminate, so spend your time analyzing these better answer choices.

Taking a Systematic Approach

What do lawyers do? They argue. They make statements and support them with evidence to convince a judge or jury that they're right or that their opponents are wrong. They read statutes, cases, and briefs, looking for tidbits of information that they can use to prove that their side is right or the other side is wrong — all under an intense time crunch.

What don't lawyers do? They don't argue from personal conviction or emotion. They don't base their arguments on their own feelings but on the facts and the laws. They don't always get to choose the side they represent, which occasionally results in a lawyer's having to support a side that she personally believes should lose. In every logical reasoning argument, the author states some conclusion and attempts to support it with evidence. Your job is to identify this conclusion, figure out how the author is supporting it, and then determine why it's successful or not.

To break down a logical reasoning question, follow these steps:

1.     Read the question.

2.     Read the argument paragraph, focusing on the specific information you need to know to answer the question and looking for inconsistencies and/or assumptions in the logic.

3.     Come up with your own idea of a possible correct answer.

4.     Evaluate the answers.

Reading the question first

Tackle a logical reasoning question by reading the question first to determine its type. Following are some of the main types of logical reasoning questions you may encounter:

·        Assumptions: Which one of the following is an assumption required by the argument above?

·        Flaws: A reasoning flaw in the argument is that the argument . . .

·        Logical conclusions: Which one of the following most accurately expresses the main conclusion of the argument?

·        Strengthen: Which one of the following, if true, most strengthens the argument?

·        Weaken: Which one of the following, if true, most seriously weakens the argument above?

·        Inference: If the statements above are true, then which of the following must also be true?

·        Role played by a claim: The claim that attorneys sometimes serve as their own secretaries plays which one of the following roles in the argument?

·        Resolving discrepancies or paradoxes: Which one of the following, if true, most helps to resolve the apparent paradox described above?

·        Disagree: The statements above provide the most support for holding that X would disagree with Y about which one of the following statements?

·        Patterns of reasoning: Which one of the following exhibits a pattern of reasoning most similar to that exhibited by the argument above?

·        Principles: Which one of the following conforms most closely to the principle illustrated by the statements above?

·        Structure of argument: In responding to Larry, Stephen . . . (criticizes, accuses, explains, challenges, assumes)

Chapters 89, and 10 show you how to distinguish logical reasoning question types. When you first read the question, don't read all the answer choices; doing so takes way too much time and clutters your thinking. Instead, concentrate just on the information you need to answer the question. Then you can read the argument with the specific question in mind. For example, if a question asks you to reconcile an apparent discrepancy, read the argument looking for a discrepancy. If a question asks you for an assumption, read the argument looking for an assumption. Reading the argument before the question doesn't hurt, but most arguments lend themselves to several different question types, and if you read the argument first and only then read the question, you may have to backtrack through the argument.

tip.eps Underlining the key words in the question may help. For example, if you get a question that asks you to resolve a discrepancy, underline the word discrepancy. If the question asks you for the author's conclusion, underline the word conclusion.

Reading the argument

After you figure out what kind of question you're dealing with, read the paragraph very carefully. Be sure to locate the argument's conclusion, which may come at the beginning, middle, or end of the paragraph. When you've identified the conclusion, you can better understand the rest of the paragraph. As you read the paragraph, look for inconsistencies or gaps in the argument that may help you answer the question. Look for whatever the question asks for. If it asks for an assumption, look for an assumption — you know one is in there. If it asks for a flaw, find a flaw. Isolating the argument's premises, assumptions, and conclusion helps you determine the method of reasoning. We cover how to go about these tasks in the later section “Making a Case: Essentials of Informal Logic.”

The argument paragraph usually isn't too complicated, and therefore, you may be tempted to read it too quickly. Force yourself to read slowly and carefully so you don't skim over the word or words that provide the keys to the argument. If you read thoroughly enough, you'll be able to eliminate some — or even most — of the answer choices. When you're down to two possible answers, you can then easily refer back to the text to make sure you choose the correct answer.

Here's an example: “My house is full of bees. I need to call an exterminator.” What's the argument's conclusion? I need to call an exterminator. What evidence is used to justify this conclusion? My house is full of bees.

This basic statement, simple though it is, could become the basis for a variety of logical reasoning–style questions. For example, what assumptions does this statement make? It assumes that an exterminator can eradicate bees in a house. What information could strengthen the conclusion? Maybe something like, “Exterminators are specialists in ridding houses of insect pests.” What information could weaken the conclusion? How about a statement such as, “Ordinary exterminators don't handle bee swarms and recommend that customers call animal control specialists to take care of them.”

tip.eps Logical reasoning questions, like all LSAT questions, include all the information you need to answer them correctly. That means you don't have to be an expert in any esoteric topic — say, bees or exterminators — to answer them. That doesn't mean, however, that you don't have to understand what they're talking about. Logical reasoning questions presume a fairly high level of reading proficiency and vocabulary; you have to be a skilled reader to understand the arguments well enough to work with them. So you should still leave your preconceived notions about a subject at home, but you should definitely keep thinking actively and put your vocabulary and reading skills to work.

remember.eps Most logical reasoning questions are a bit longer than this example, and they're usually not as straightforward. At heart, though, they're not that different. Each one offers a proposition and supports it with evidence. The proposition may be right or wrong, and the evidence may or may not support it, but the basic structure doesn't change.

Again, if it helps you to underline key words, underline them. Be careful, though, because you don't want to underline too much, which won't help you. If you're a chronic underliner or if you find the exercise of underlining to be distracting, forget about it and just read carefully.

remember.eps LSAT arguments seem like fairly scholarly or specialized statements, but they're really just made-up paragraphs. So if their facts seem wrong or if an argument makes a point that you disagree with, don't let it bother you. You need to find the argument structure, that's all. Forget about the actual accuracy of the facts — it doesn't matter.

Formulating an answer

Now try to answer the question in your head before you read the answer choices. If you do, the correct answer may just jump right out at you. The wrong answers will be glaringly wrong, and crossing them off should take no time.

Of course, you can't always concoct the exact right answer. For example, if a question asks what information would strengthen the author's conclusion, you can't always hope to imagine the exact factoid that'll be in the right answer, but you probably can come up with something in the ballpark. Actively approach the answers already armed with an idea of what you want to find.

remember.eps Many students overlook this step, not realizing what a valuable tool anticipating the answer can be. Don't make this mistake yourself. Always try to concoct an answer before you check out the choices. Paraphrasing the right answer in your head saves time in the long run. The answer choices are meant to confuse you, but if you have a solid idea of what you're looking for, the right answer will appear more obvious, and you won't be lead astray by wrong choices.

tip.eps You can't answer one kind of question beforehand: a question that asks you which of the five answer choices is most similar to the pattern of reasoning in the argument. You can, however, break down the pattern of reasoning before you confront the choices, so really you're still coming up with an answer first. See Chapter 9 for more information.

Reading the answers and eliminating the wrong ones

Now read the answers. Having one obviously correct choice and four obviously wrong ones would be nice, but of course, the LSAT doesn't work that way. All five choices seem plausible. The LSAT-makers want you to spend your time agonizing over the answer choices, fretting because two of them look right and you just can't figure out which is which. Remember, though, there are never two right answers. Four answers are always wrong, one answer is always right, and the test-makers have to be very clear about which is which. Choices that seem ambiguous really aren't.


The winding or the straight road?

Do you work logical reasoning sections straight through, from first to last question? Or does it make more sense to jump around, answering the questions you like first and saving the ugly ones for later?

We don't think it matters. There's no reason not to begin on the first question and work your way to the last, filling in the dots on your answer sheet as you go. Then again, if you find jumping around easier, go for it. And if you get stuck on a question, it makes sense to skip it and move on, coming back later if you have time. Just be sure not to mess up your answer sheet. Use your finger or pencil to point to the answer you want to bubble in, or some other technique that keeps your answers matched up. (See Chapter 2 for more on this topic.)

If you do jump around, realize that rating questions for difficulty uses up some of your valuable test time. There's not all that much variation in difficulty from problem to problem, so you may get better results just tackling each question without categorizing it first.


Even when you know which answer you want to find, reading through all the choices may take a little time. Logical reasoning answer choices can sometimes be nearly as long and complicated as the actual arguments. You know what to do, though: Read each answer quickly but carefully. Cross it off if you know for sure that it's wrong; leave it alone if you think it may be right.

remember.eps Don't get too caught up in the quest for speed. If you feel like you need to read an argument twice to find the answer, go ahead and do it, and don't fret because you had to backtrack. You've already put the time into reading the argument, so you may as well give it a fair shake.

After reading all the answer choices, pick an answer. If you cross off four obviously wrong answers and find one obviously correct one, great. If you can't decide between two answers, think about them for a little while, no more than 30 seconds or so. If you still can't decide which one is right, pick one and move on. You have other fish to fry.

tip.eps Take a break after each page. Your brain gets tired after several straight minutes of logical reasoning. These questions are tiring because there are so many of them and because you're constantly stuffing new information into your already overstuffed mind. So every time you finish a page of questions, take a break. Not a long break — just a few seconds is enough. Close your eyes, roll your head around, stare out the window, and let your brain recharge. Then forge ahead.

warning.eps While you look around the room or out the window, be sure you don't look at anyone else's test or even seem like you may be. LSAT proctors don't tolerate even a suspicion of cheating. If you cherish hopes of a legal career, you won't ever cheat or look like you're cheating on the LSAT.

Making a Case: Essentials of Informal Logic

You can score well on the LSAT logical reasoning questions without knowing the elements of informal logic, but if you understand a few terms and concepts, you'll score even higher. You really just need to know the two basic components of a logical argument and a few methods of coming up with a conclusion.

Fighting fair: The elements of an argument

A logical argument consists of premises and a conclusion, and when you're analyzing arguments, identifying what parts are premises and what makes up the conclusion can help. The premises give the supporting evidence that you can draw a conclusion from. You can usually find the conclusion in the argument because it's the statement that you can preface with “therefore.” The conclusion is often, but not always, the argument's last sentence. For example, take a look at this simple argument:

·        All runners are fast. John is a runner. Therefore, John is fast.

The premises in the argument are “All runners are fast” and “John is a runner.” You know this because they provide the supporting evidence for the conclusion that John is fast, which is the sentence that begins with “Therefore.” Not all conclusions in LSAT arguments begin with “therefore” or other words like it (such as “thus” and “so”), but you can try adding “therefore” to any statement you believe is the conclusion to see whether the argument makes sense.

Getting from point A to point B: Types of reasoning

Each logical argument has premises and a conclusion, but not every argument comes to a conclusion in the same way. For the purposes of the LSAT, you should be familiar with two basic types of logical reasoning: deductive and inductive. LSAT logical reasoning questions primarily test your inductive reasoning ability.


Sure seems Greek to me: Origins of logical thought

Legend has it that a Greek philosopher named Parmenides in the fifth century BC had plenty of time on his hands while living in a Greek colony off the west coast of Italy. So he whiled away the hours contemplating logical thought and became one of the first Westerners to record his findings. He penned a philosophical poem in which an unnamed goddess instructs him in the ways of determining truth about the universe. His poem explored the contrast between truth and appearance and portrayed truth to be firm and steadfast, whereas appearance (the way mortal men usually think) was unstable and wavering. Parmenides's work influenced other great Greek thinkers, like Plato, Aristotle, and Plotinus.

Unfortunately, you won't have a goddess to guide you through the LSAT's logical reasoning questions, but you can rely on Aristotle's method of developing syllogisms to examine LSAT arguments. He's the one who came up with this famous syllogism: All humans are mortal; Socrates is human; therefore, Socrates is mortal.


Elementary, my dear Watson: Deductive reasoning

In deductive reasoning, you come up with a specific conclusion from more-general premises. The great thing about deductive reasoning is that if the premises are true, the conclusion must be true! The following is an example of a deductive reasoning argument:

·        All horses have hooves. (General premise)

·        Bella is a horse. (More specific premise)

·        Therefore, Bella has hooves. (Very specific conclusion)

If the premise that all horses have hooves is true, and if Bella is, in fact, a horse, then it must be true that Bella has hooves. The same holds true for all examples of deductive reasoning. Here's another example:

·        All who take the LSAT must complete a writing sample. (General premise)

·        You're taking the LSAT. (More specific premise)

·        Therefore, you have to complete a writing sample. (Very specific conclusion)

This example shows the relationship between the truth of the premises and that of the conclusion. The first premise is categorically true: The LSAT requires you to write an essay. The second premise, however, may not be true. Certainly, you're thinking of taking the LSAT or you wouldn't be reading this book, but you may still decide not to take the test. This possibility doesn't affect the argument's logic. Remember, in deductive reasoning, the conclusion must be true if the premises are true. If you take the test, you have to write an essay, so this argument is valid.

Perhaps I'm just generalizing: Inductive reasoning

In deductive reasoning, you draw a specific conclusion from general premises. With inductive reasoning, you do just the opposite; you develop a general conclusion from specific premises. Inductive reasoning differs from deductive reasoning in that the conclusion in an inductive reasoning argument could be false, even if all the premises are true. With inductive reasoning, the conclusion is essentially your best guess. That's because an inductive reasoning argument relies on less complete information than deductive reasoning does. Consider this example of an inductive argument:

·        Bella is a horse and has hooves. (Specific premise)

·        Smoky is a horse and has hooves. (Specific premise)

·        Nutmeg is a horse and has hooves. (Specific premise)

·        Shadow is a horse and has hooves. (Specific premise)

·        Therefore, it is likely that all horses have hooves. (General conclusion)

Because an inductive argument derives general conclusions from specific examples, you can't come up with a statement that “must be true.” The best you can say, even if all the premises are true, is that the conclusion can be or is likely to be true.

tip.eps Inductive reasoning arguments come in all sorts of flavors, but the folks who create the LSAT tend to favor three types: cause and effect, analogy, and statistical. To excel on the LSAT, you want to get familiar with these three methods of inductive reasoning:

·        Cause-and-effect arguments: This argument concludes that one event is the result of another. These types of arguments are strongest when the premises prove that an event's alleged cause is the most likely one and that there are no other probable causes. For example, after years of football watching, you may conclude the following: “Every time I wear my lucky shirt, my favorite team wins; therefore, wearing my lucky shirt causes the team to win.” This example is weak because it doesn't take into consideration other, more probable reasons (like the team's talent) for the wins.

·        Analogy arguments: This argument tries to show that two or more concepts are similar so that what holds true for one is true for the other. The argument's strength depends on the degree of similarity between the persons, objects, or ideas being compared. For example, in drawing a conclusion about Beth's likes, you may compare her to Alex: “Alex is a student, and he likes rap music. Beth is also a student, so she probably likes rap music, too.” Your argument would be stronger if you could show that Alex and Beth have other similar interests that apply to rap music, like hip-hop dancing or wearing bling. If, on the other hand, you show that Alex likes to go to dance clubs while Beth prefers practicing her violin at home, your original conclusion may be less likely.

·        Statistical arguments: This argument relies on numbers to reach a conclusion. These types of arguments claim that what's true for the statistical majority is also true for the individual (or, alternately, that what's true of a member or members of a group also holds true for the larger group). But because these are inductive reasoning arguments, you can't prove that the conclusions are absolutely true. When you analyze statistical arguments on the LSAT, focus on how well the given statistics apply to the conclusion's circumstances. For instance, if you wanted people to buy clothing through your website, you may make this argument: “In a recent study of consumers’ preferences, 80 percent of shoppers surveyed said they prefer to shop online; therefore, you'll probably prefer to buy clothes online.” You'd support your conclusion if you could show that what's true for the majority is also true for an individual.

tip.eps To do well on logical reasoning questions, you need to recognize stated premises, assumed premises, and conclusions in arguments; determine the method of reasoning; and establish whether premises adequately support the conclusion. As you can induce, knowing a little about logical reasoning is essential to scoring well on the LSAT!