Category: Flaws

There are many LSAT questions that involve causal reasoning, which is significantly different from the conditional reasoning that makes up most of the rest of the test. PowerScore’s Logical Reasoning Bible squeezes in a chapter on causal reasoning between the chapter on “weakening arguments” and “strengthening arguments.” There’s a reason for that–a statement which might a perfectly valid conditional statement (“if the rooster crows, then the sun comes up”) could be a ridiculous causal claim (“the rooster crows, which causes the sun to come up”).

PowerScore identifies five situations which weaken a causal relationship. I have taken the liberty of turning them into an acronym:

• R: Reverse causation
• A: Alternate cause
• C: Cause without effect
• E: Effect without cause
• S: Statistical errors

Let’s run through these, using our rooster example. Perhaps the rooster does not cause the sun to come up–instead, it is the early morning sunlight that causes the rooster to crow. That would be a clear case of reverse causation.

The problem with that explanation, as any chicken keeper knows, is that roosters start crowing long before the sky begins to get light. Maybe there is some kind of biological clock inside the rooster that tells it that 24 hours have passed. If so, that would be an alternate cause–something other than the sun itself that causes the effect.

If we wanted to prove that the rooster doesn’t really make the sun come up, we just need to get the rooster to crow in the middle of the night and see what happens. This happens to me now and then when we start something time consuming right around sunset. I have to grab my flashlight and go close up the chickens late at night. My roosters start crowing their heads off when I turn on the lights, and the sun stays put.  It’s hard to have a causal relationship if you you can have the “cause” (the rooster crowing) without the “effect” (the sun coming up). That’s a cause without effect situation.

Most of my students don’t even keep chickens–which means the sun comes up on them even though no rooster crowed.  That is an effect without cause situation.

PowerScore’s final category involves statistics. When we say, “The rooster crows and the sun comes up,” we oversimplify the situation. My roosters crow pretty much all day long. (That’s why we keep them well away from the house!) If we graphed all the times each rooster crows and plotted it against the sunrise, it would be obvious that the rooster has nothing to do with the sunrise. The reason I associate sunrise with roosters is that when those noisy birds wake me up I want to go make rooster soup! If I’m already awake, I just ignore their crowing. If I had good data instead of my very selective memory, I would never associate crowing with sunrise.

More students get more flaw questions wrong than anything else. (That’s because flaw questions are hard for many people, flaw answers are hard for most people, and there are lots of flaw questions on every test.) Every LSAT curriculum includes a chapter on flaws, but nothing that I have seen in print will enable a student to dramatically improve on flaw questions. That’s a pity, because flaws–more than any other question type–can be conquered with sufficient time and effort.

I want all my students to get every flaw question right every time. To achieve that goal, I start with the answer choices. Every LSAT flaw question has five different answers, and the overwhelming majority of those answers describe specific errors that any student can learn to identify with a little help and a lot of practice.

It’s a little like bird-watching. Here’s an example:

There’s a bird at my bird-feeder. It’s small bird, all black, gray, and white. There’s some white on its cheeks  but the top of its head and the underside of its chin is black.  I see plenty of them every winter, but the only time I’ve seen one in summer was up in Maine.

1. Chickadee
2. Nuthatch
3. Flicker
4. Junco
5. Cardinal

Most readers can probably rule out a cardinal instantly, but the rest of the options are harder. Most readers are going to have to click the hyperlinks to look at the pictures before they can identify this bird. But once you know exactly what these five birds look like, it’s (fairly) easy to pick the right one from the list.

Once you know your flaws, you can eliminate wrong answers in a hurry.  In our bird example above, only two of those five birds are white and gray and black. One of the others is a dark gray and white, but there’s no white on the head so it isn’t an option. Of the two that really are white and gray and black, one is migratory and the other isn’t. Any decent bird-watcher could pick the right answer in about five seconds without ever needing to click on a hyperlink. I want you to be that fast (and that accurate) on flaw questions.

The following work-in-progress is a hyperlinked list of the ANSWERS to flaw questions in “10 Actual Official LSAT Preptests Volume V.” This document should immediately increase your accuracy on flaw questions by explaining what each answer means. If you carefully study the different flaws and the words the LSAT authors use to describe it, you should be able to get more right answers in less time in the LSAT logical reasoning section,

I recommend that this document be used as part of the 7Sage “blind review” method. Try to figure out each flaw question on your own, and then, without checking your  answer, look at that question in this document.  If you aren’t familiar with the labels I use  to describe the different flaws, just click the hyperlink to see what Wikipedia or other authors have said about this specific flaw. Then, after you are clear on what each answer actually means, choose your answer. If it is the same answer you originally chose, congratulations! If you changed your answer, congratulations again–you may have just learned something that will help you get into the law school of your choice!

62-2-5: Childhood lead poisoning (p. 17)

1. Statistical errors
2. Circular reasoning
3. Overlooked possibility
4. Assumption
5. Assumption

62-2-7: Flawed parallel pattern (p. 17) is fallacy of division

62-2-8: Space exploration (p. 18)

1. Fallacy of composition
2. Possibility v. Certainty
3. Possibility v. Certainty
4. Possibility v. Certainty
5. Argument from ignorance

62-2-11: Athlete’s foot (p. 19)

1. “Can cure” does not equal “always cures”
2. Survey problem
3. Assumption
4. Overlooked possibility
5. Assumption

62-4-9: Parallel flawed pattern (p. 30) is “if a husband is right-handed, the wife is probably right-handed; so if the wife is left-handed, the husband is probably left-handed.”

62-4-10: Moon of Jupiter (p. 30) [THIS NEEDS WORK!]

1. Assumption (that a “necessary” condition is always necessary–this assumption is always true!)
2. Overlooked possibility
3. Assumption
4. Overlooked possibility
5. Assumption

62-4-

1. X

62-4-

1. X

62-4-

1. X

62-4-

1. X

Most of my students with 7Sage.com accounts quickly discover that their highest study priority in logical reasoning should be “flaw” questions. With seven or more flaw questions per test and five confusing answers per question, most students will spend at least six minutes on LSAT day just trying to figure out what those flaw answers are supposed to mean. Every answer you don’t recognize consumes time, adds stress, and increases your odds of picking the wrong answer.

Students can improve both speed and accuracy by learning how to quickly and accurately recognize what the different flaw answer choices mean. The faster you can dismiss a wrong answer, the faster you can find the right answer and move on. A student who can quickly identify the wording used to describe common flaws should gain enough time to do at least two more questions in each logical reasoning section–and may be able to get more of the flaw questions right in the process. That can raise your score on test day significantly!

I have asked many students to study these flaw answer choices on  their own–with disappointing results. If you don’t know what the various flaws are, it’s really hard to figure out what these answer choices mean.  I have yet to find a commercially available LSAT text that enables the average student to quickly, confidently, and accurately identify the different answer choices.

They say it is better to light a single candle than to curse the darkness, so this series of posts is my attempt to light the way for a new generation of law students. I hope to identify every flaw answer choice in every “10 Actual Official LSAT Preptest” book. Here’s what I’ve done so far:

• Index of Flaws
• 10 Actual Official LSAT Preptests: Volume VI

 

 

Master Index of Flaws

1. Ad hominem
2. Alternate cause
3. Appeal to authority
4. Appeal to emotion
5. Appeal to the people
6. Argument from ignorance
7. Assumption
8. Circular reasoning
9. Correlation does not imply causation
10. Equivocation
11. Fallacy of composition
12. Fallacy of division
13. False dilemma
14. Genetic fallacy
15. Hasty generalization
16. Internal contradiction
17. Is/ought problem
18. Mistaken most
19. Mistaken negation
20. Mistaken reversal
21. No true Scotsman
22. Numbers v. Percents
23. Overlooked possibility
24. Possibility v. Certainty
25. Reverse causation
26. Straw man
27. Subjective/objective problem
28. Survey problem
29. Unrepresentative sample

PowerScore has trademarked a remarkable number of terms that have become standard LSAT jargon, including the term “Mistaken Negation (TM).” This logical error was identified more than two thousand years before PowerScore trademarked the name, however. Aristotle listed “denying the antecedent” as one of the thirteen original fallacies. Whatever we call this error, it shows up whenever you find this pattern:

• If you live in Detroit, you live in Michigan
• Therefore, if you don’t live in Detroit, you don’t live in Michigan.

This error is obvious when you use an intuitive example involving geography, but it is less obvious in other contexts. Don’t let that keep you from looking for it every chance you get–this little error is easy to slip into an argument and hard for the untrained eye to spot. That means you’ll see lots of these errors in easy-to-medium flaw questions.

You’ll see this answer choice often, but it may be the hardest answer to make sense of. The LSAT writers often use abstract terms that tend to paralyze the student. While it is possible to decode these baffling answers and demonstrate that they describe a “mistaken negation (TM),” it is very hard to do that with the clock ticking and your future on the line. That’s why it is so important to learn to identify this and other flaw answers before test day.

Here are some examples of answers that describe this particular flaw. (These are not actual LSAT answers, due to copyrights, but they are inspired by and similar to real answers):

• “It treats a sufficient condition for an argument’s conclusion to be a necessary condition for that conclusion.”
• “Takes a sufficient condition to be a necessary condition.”
• “Mistakes something that is sufficient to make an argument invalid for something that is necessary to make that argument invalid.”

Basically, these answers all indicate that somebody confused a sufficient condition for a necessary condition. That sounds a lot like a “mistaken reversal (TM)” (which is what happens when you confuse a necessary condition for a sufficient condition), but it is different. If you think a condition is necessary, then not having that condition means you can’t have the other condition.  Here’s how that works out:

• If you live in Detroit, you live in Michigan (true)
• If you live in Michigan, you live in Detroit (false–you confused the necessary term for a sufficient term)
• If you don’t live in Detroit, you don’t live in Michigan (false–you confused the sufficient term for a necessary term by saying what would happen if you didn’t have that term)

PowerScore has trademarked a remarkable number of terms that have become standard LSAT jargon, including the term “Mistaken Reversal (TM).” This logical error was identified more than two thousand years before PowerScore trademarked the name, however. Aristotle listed “affirming the consequent” as one of the thirteen original fallacies. Whatever we call this error, it shows up whenever you find this pattern:

• If you live in Detroit, you live in Michigan
• Therefore, if you live in Michigan, you live in Detroit.

This error is obvious when you use an intuitive example involving geography, but it is less obvious in other contexts. Don’t let that keep you from looking for it every chance you get–this little error is easy to slip into an argument and hard for the untrained eye to spot. That means you’ll see lots of these errors in easy-to-medium flaw questions.

You’ll see this answer choice often, but it may be the hardest answer to make sense of. The LSAT writers often use abstract terms that tend to paralyze the student. While it is possible to decode these baffling answers and demonstrate that they describe a “mistaken reversal (TM),” it is very hard to do that with the clock ticking and your future on the line. That’s why it is so important to learn to identify this and other flaw answers before test day.

Here are some examples of answers that describe this particular flaw. (These are not actual LSAT answers, due to copyrights, but they are inspired by and similar to real answers):

• “It mistakes a situation that must be present to establish the validity of the conclusion for a situation that would guarantee the validity of the conclusion.”
• “It treats a requirement for a pig to fly as something that ensures that a pig will fly.”
• “It takes a necessary condition for an argument’s failure to be a condition that would guarantee the argument would fail.”
• “Concludes, from the fact that X occurred and that Y would ensure that X occurred, that Y must have occurred.”

In most cases, the answer simply states that somebody has mistaken a necessary condition for a sufficient condition. Until you become familiar with the underlying problem and the way the LSAT writers word these “mistaken reversal (TM)” answers, these can be baffling. After you recognize the problem and the pattern, they become quite simple.

“Most” is a common and dangerous word on the LSAT. I routinely tell students that “‘most’ is mostly wrong” because there are so many easy ways to write a wrong answer using “most.” It is no wonder, then, that one of the most common parallel flaw patterns is the “mistaken most.” Here are some examples:

Most mammals have four legs.
All dolphins are mammals.
THEREFORE most dolphins have four legs.

Most mammals have four legs.
Dolphins do not have four legs.
THEREFORE dolphins probably aren’t mammals.

Most Congressmen live near Washington, DC.
Most US citizens don’t live near Washington, DC.
THEREFORE, there must be more Congressmen than citizens near Washington, DC.